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So my lovely wife bought me a Samsung Galaxy Tab 4 for Father's Day and I've been loving it ever since. Just as other with Samsung products, the Galaxy Tab 4 has the ability to add a microSD card to expand the memory on the device. Since it's been over a year, I decided to do some more research to see if SanDisk offered anything new. As of 6/19/2014, their product lineup for microSD cards from worst to best (performance-wise) are the as follows:
SanDisk Ultra
SanDisk Ultra PLUS
SanDisk Extreme
SanDisk Extreme PLUS
SanDisk Extreme PRO

Now, the difference between all of these cards are simply the speed in which you can read/write data to the card. Yes, the published rating of most all these cards (except the SanDisk regular) are Class 10/UHS-I but that's just a rating... Actual real world performance does get better with each model, but with faster cards come more expensive prices. Since Amazon doesn't carry the Ultra PLUS model of microSD card, I had to do direct comparisons between the SanDisk Ultra ($34.27), Extreme ($57.95), and Extreme PLUS ($67.95).

As mentioned in my earlier review, I purchased the SanDisk Ultra for my Galaxy S4. My question was, did I want to pay over $20 more for a card that is faster than the one I already owned? Or I could pay almost double to get SanDisk's 2nd-most fastest microSD card.

The Ultra works perfectly fine for my style of usage (storing/capturing pictures & HD video and movie playback) on my phone. So in the end, I ended up just buying another SanDisk Ultra 64GB card. I use my cell phone *more* than I do my tablet and if the card is good enough for my phone, it's good enough for my tablet. I don't own a 4K HD camera or anything like that, so I honestly didn't see a need to get one of the faster cards at this time.

I am now a proud owner of 2 SanDisk Ultra cards and have absolutely 0 issues with it in my Samsung devices.

I haven't had to buy a microSD card in a long time. The last time I bought one was for my cell phone over 2 years ago. But since my cellular contract was up, I knew I would have to get a newer card in addition to my new phone, the Samsung Galaxy S4. Reason for this is because I knew my small 16GB microSD card wasn't going to cut it.

Doing research on the Galaxy S4, I wanted to get the best card possible that had decent capacity (32 GB or greater). This led me to find that the Galaxy S4 supports the microSDXC Class 10 UHS-I card, which is the fastest possible given that class. Searching for that specifically on Amazon gave me results of only 3 vendors (as of April) that makes these microSDXC Class 10 UHS-1 cards. They are Sandisk (the majority), Samsung and Lexar. Nobody else makes these that are sold on Amazon.

Seeing how SanDisk is a pretty good name out of the 3 (I've used them the most), I decided upon the SanDisk because Lexar was overpriced and the Samsung one was overpriced (as well as not eligible for Amazon Prime).

But the scary thing is that when you filter by the SanDisk, you literally get DOZENS of options. All of them have different model numbers, different sizes, etc. Then there's that confusion of what's the difference between SDHC & SDXC?

SDHC stand for "Secure Digital High Capacity" and SDXC stands for "Secure Digital eXtended Capacity". Essentially these two cards are the same with the exception that SDHC only supports capcities up to 32GB and is formated with the FAT32 file system. The SDXC cards are formatted with the exFAT file system. If you use an SDXC card in a device, it must support that file system, otherwise it may not be recognizable and/or you have to reformat the card to FAT32.

FAT32 vs exFAT:
The differences between the two file systems means that FAT32 has a maximum file size of 4GB, limited by that file system. exFAT on the otherhand, supports file sizes up to 2TB (terabytes). The only thing you need to know here really is that it's possible your device doesn't support exFAT. If that's the case, just reformat it to FAT32. REMEMBER FORMATTING ERASES ALL DATA!

To clarify the model numbers, I I hopped over to the SanDisk official webpage. What I found there is that they offer two "highspeed" options for SanDisk cards. These are SanDisk Extreme Pro and SanDisk Ultra. SanDisk Extreme Pro is a line that supports read speeds up to 95MB/sec, however they are SDHC only. To make things worse, they are currently only available in 16GB & 8GB capacities. Since one of my requirements was to have a lot of storage, I ruled these out.

The remaining devices listed on Amazon's search were the SanDisk Ultra line. But here, confusion sets in because SanDisk separates these cards to two different devices. Cameras & mobile devices. Is there a real difference between the two or is this just a marketing stunt? Unfortunately I'm not sure but I do know the price difference between the two range from a couple cents to a few dollars. Since I wasn't sure, I opted for the one specifically targeted for mobile devices (just in case there is some kind of compatibility issue). To find the exact model number, I would go to Sandisk's webpage (sandisk.com) and compare their existing product lineup. From there, you get exact model numbers and you can then search Amazon for these model numbers. That is how I got mine (SDSDQUA-064G).

As for speed tests, I haven't run any specific testing, but copying 8 GB worth of data from my PC to the card literally took just a few minutes.

One last note is that Amazon attaches additional characters to the end (for example SDSDQUA-064G-AFFP-A vs SDSDQUA-064G-U46A). The difference between the two is that the "AFFP-A" means "Amazon Frustration Free Packaging". Other than that, these are exactly the same. If you're wondering what I got (and want to use it in your Galaxy S4), I got the SDSDQUA-064G-u46A and it works like charm.
5150+ comments| 2,250 people found this helpful. Was this review helpful to you? Report abuse
I have tested dozens of SDHC and micro-SDHC cards. One disturbing trend I noticed is that: the speed class rating for micro-SDHC is typically inflated. For example, a 'class-10' rating means the card must deliver a sequential write speed of at least 10MB/s. But somehow, a class-10 microSDHC cards is always slower than a class-10 SDHC card from the same manufacturer. Case in point: the PNY 32 GB microSDHC Card (P-SDU32G10-EFS2) claims to be 'class-10', yet it can only write at 8.6MB/s maximum, while the full-size PNY P-SDHC16G10 achieved 13.4MB/s according to CrystalDiskMark v3.01.

This SanDisk Ultra 32 GB microSDHC Class 10 UHS-1 card (SDSDQUA-032G-U46A), however, proves to be the exception. It achieved a sequential write speed of over 10MB/s according to two different benchmark programs (11.8MB/s in "CrystalDiskMark", 10.6MB/s in "H2testw v1.4"). This is faster than all my other microSDHC cards, including two 'class-10' cards from PNY and Polaroid.

A closer look at the file transfer speed using "Flash Memory Toolkit" revealed another nice surprise: For writing small files, this Sandisk Ultra microSDHC card performed just as well as its full-size counterpart, the SanDisk Ultra SDHC (SDSDU-032G-AFFP). In contrast, all my other class-10 microSDHC cards perform poorly while writing smaller files. See the benchmark results I uploaded to 'Customer Images' for details.

When you use a memory card in a digital camera to record HD video, it needs to store a huge video file each session. That means its sequential write speed is most critical. When used in a tablet or a smart phone, however, the card's random write speed for small files is more important. That's why in such applications, the Sandisk microSDHC will perform faster than the PNY and Polaroid cards, even though they are also rated as 'class-10'.

[Bottom Line]
As of this writing, the Sandisk Ultra microSDHC card ia actually priced lower than other class-10 cards from PNY and Polaroid. This makes the Sandisk the best value - especially if you need honest class-10 performance across all platforms.

[Side Notes]
- Do not confuse this Sandisk Ultra card with SanDisk Mobile Ultra microSDHC (SDSDQY-032G-U46A). The latter is rated for class-6 only.
- The size of this '32GB' card is 29.7GB according to my computer. This is actually normal because computer people count one Gig as "2 to the power 30", which is 7.3% larger than one billion. So 29.7GB translates to 31.9 billion bytes, which is '32GB' according to marketing people.

[Update on Feb 4, 2013]
1. Amazon combined the Sandisk Ultra 32GB and 64GB cards on the same product page. Please beware that your intended appliance must be compatible with 'SDXC' in order to used the 64GB version. My original review refers to the 32GB 'SDHC' version.

2. There are two part numbers for the same card. If you start from the Amazon product page and select 'Retail Packaging', you'll see the part number of SDSDQUA-032G-U46A. But if you click on 'Frustration Free Package', the part number changes to SDSDQU-032G-AFFP-A.

[Update on Oct 5, 2013]
The Sandisk microSDHC card works great in my new Samsung Galaxy S3, without the need for reformat (the default format is FAT32)

[Update on Dec 26, 2013]
My old test results were limited by the card reader and USB 2.0 port used. I re-tested the Sandisk UHS1 micro card using the Transcend RDF5 Card Reader connected to an USB 3.0 port. Here are the results from 'CrystalDiskMark 3.01 x64':
- Sequential Read speed = 40.0MB/s (was 34.8MB/s when connected to USB 2.0 port)
- Sequential Write speed = 13.1MB/s (was 12.6MB/s when connected to USB 2.0 port)
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5150+ comments| 1,617 people found this helpful. Was this review helpful to you? Report abuse
on April 14, 2014
I for one have not bought into Google's, or anybody else's, idea that streaming everything is so great. With all the regressive data caps and sketchy throughput, I never want to rely on something being available to me online. Much better to have it local. And with this new card I can finally pack all of my music (~56GB), all of my photos, dozens of reference ebooks, and a few videos to boot and still I have around 9GB free as breathing room for my podcatcher. The only real bummer with this card is the speed. Just as I got acclimated to SanDisk's 64GB Extreme Plus level of speed, going back to ordinary class 10 speed that this card has is a little painful. Luckily playing music or even playing videos doesn't oversaturate the read performance. What WILL trip you up however is doing a straightforward copy or move operation while you're listening to something. This card does not seem to handle multiple simultaneous operations without something going awry. So long as you understand it's limitations and you can live with them, the enormous amount of storage you can pack into your phone or tablet is very welcome.

So far I've used one of these in a Samsung Galaxy Note 2 N7100, LG G Pad, and a Sony Xperia Z1 Compact - all with success.
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on April 22, 2016
Physical Design and Speeds
The 64GB microSDXC is red and blue, a bright change from existing black memory cards. That makes it harder to lose. As someone that uses (and loses) microSD cards on a regular basis, I can tell you that this simple change in color makes a big difference. It also looks snazzy.

If this is your first microSD card, you should know that it's really, really tiny, about the size of the size of your pinky nail. It comes with an adapter that allows you to use the card in any SD slot, so it'll work with digital cameras and be easily readable in computers.

The actual amount of space available on the card is 59.46GB. It's faster than most phone and tablet memory cards, with Class 6 speeds of up to 30MBps. I tested the read and write speeds using the Antutu benchmarking app on a number of Android-based smartphones. The read speeds consistently reached 30MB and slightly above for each test, while the write speeds averaged out to 13.5MBps. That's about identical to the results I got for a 32GB microSDHC card.

Compatibility and Conclusions
My biggest fear was compatibility. Most phones support microSDHC, which maxes out at 32GB. MicroSDXC is the new standard announced in 2009 that allows small memory cards like this to support storage sizes up to 2TB. The thing is, current phones don't have SDXC slots. Luckily, the card worked in every phone I tested it with. I threw it into a Motorola Droid Bionic, Samsung Galaxy S III, and a Sony Ericsson Xperia Play 4G, and it worked without a hitch each time. I also tried it with a Motorola Droid (4 stars), to see how it would work in an older device. Again there was no problem, and each phone was able to recognize the card at its full capacity, as well as read and write without a problem.

The card also worked fine in multiple Windows 7 PCs and a 27-inch iMac. One Lenovo Windows 7 laptop had a problem reading the card using the included SD adapter, but that laptop also couldn't read a 32GB MicroSDHC card.

If you're considering the 64GB SanDisk Ultra microSDXC card, it ultimately comes down to two questions. Do you need this much storage, and are you willing to pay for it? If you listen to lots of music, capture HD video, and take a bunch of photos, the microSDXC doubles the amount of storage available to you. And it may be costly, but it's less expensive than a brand-new iPod Classic.
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on August 5, 2013
NOTE: please read the last update (scroll to the bottom) - I'm leaving this review as 1 star as it appears to help others who purchased and had a similar experience.

I give SanDisk 5 stars for customer service and 1 star for the product (for those manufactured in the past) For those newly manufactured products that contain the software ROM fix, I'd give the product 5 stars.

To all those who purchased this card due to all the great reviews.... and then used it in a Galaxy S4 (GS4) smartphone for storage, the solution to the problem is not one you can solve without returning the card to SanDisk for a replacement under warranty. Believe me I tried everything that the Google searches returned as solutions... formatting as exFAT, formatting in the GS4 then copying data to the card while in the phone etc.... nothing worked... and so now please stop pulling out your hair and hopefully you will get the same result which I hope to get soon (just RMA'd and will send it back tomorrow for a free replacement under warranty).

The problem (As confirmed from the SanDisk customer support rep when I asked specifically asked him):

- When used in the GS4, this card will unmount itself inadvertently (may be true only for cards manufactured before the ROM patch described below was implemented in manufacturing). This can cause the data to become corrupt (luckily was not my experience) and / or can be very frustrating as most of us are saving 13 MP camera pictures to the card (or MP4 movies that stop in the middle of the movie) and it unmounts when you view the picture in the gallery or worse, right when you take the picture (this was the issue I experienced).

- SanDisk knows about this issue. Again, SANDISK KNOWS ABOUT THE ISSUE AND WILL REPLACE YOUR CARD. Call them (info below) and they WILL take care of it under warranty. They have a good name for a reason and they want to keep it. (sorry SanDisk about the 1 star, but I thought it was the way to get the message out to those searching for a solution)

- The customer rep told me that SanDisk tried to work with Samsung to resolve the issue but Samsung refused to acknowledge a problem exists with this card and some of their phones (especially their flagship GS4 phones).

- The customer rep told me that to their knowledge the card works fine in regular cameras (not Samsung GS4 phones with cameras, obviously) and even worked fine in some phones from HTC etc. that could accommodate the 64 GB cards. Hence the 5 star ratings from others.

- The solution SanDisk came up with was to write a patch into the ROM of the card itself to specifically address the issue on Samsung GS4 phones (and maybe other Samsung phones like the GS3). I was assured that the new card I would get would work flawlessly. will see in about 3 weeks.

- I purchased my card from Amazon June 2013, so the ones currently being manufactured and the one I should get will have the new patch. However, as SanDisk manufactures in batches (like most of the industry), old batches of "unpatched" cards obviously exist in warehouses.

- I asked about a software patch I could download and was told it's not possible... hence the "hard coded patch" in the card's ROM

So... how to take care of the problem....

After speaking with the SanDisk US customer support (link and info below), this is what I learned and did.
Go to the SanDisk site

1) [...]
2) call consumer products support (this is the US no.) 1-866-SANDISK (726-3475)
3) Tell them that the card is unmounting itself in your GS4 (I assume this is also a problem experienced by GS3 owners too)
4) They will then confirm your information, approve your return (10-15 min approval window by mine was basically instantaneously), and then send you emails with a UPS return label and instructions.
5) BTW, they also asked if I had a magnifying glass to ID the serial no. on the card, but I didn't and couldn't read it myself (those numbers are super small printed into the plastic... don't believe me? take a look yourself.) I told the rep I couldn't read them and he said no problem, they would process without the serial no. I assume this is because they send you a new replacement card only when they receive your card you send in. Makes sense.

Well, that's it. Problem (hopefully) solved. Let's see in 2-3 weeks. The rep was super nice about it and seemed like they were all too familiar with the problem. KUDOS TO SANDISK FOR TAKING CARE OF IT... however, it would be nice if there was some type of communication / notice of the issue besides Google info sources, forums etc. I spent hours, maybe a couple of days total hours worth, thinking it was an issue with my phone / my data transfer. oh well, that's how it goes.

I really hope that this review helps some of you out there with the same problem as me. GOOD LUCK!!

(btw, I'd give the card 5 stars if this problem was solved in the patched ROM of newer cards as the data transfer speeds are awesome on the card (tested transferring data via a card reader hooked to my computer)... if the data transfer / remaining mounted in the GS4 issue never existed (pre-patch of ROM, of course))

UPDATE: 08/17/2013 - All went well with the return of the SanDisk Storage card. UPS shipping took about 2 days from when I sent it, SanDisk verified the warranty claim 1 day later and 5 hours later that same day, my replacement card had been shipped. waiting on the new card now, but expect to test it out very soon (early next week). will update the post after testing out the new card. Just as a reference, I've been using a 32GB Micro SD HC SanDisk card in the GS4 since having shipped the 64GB card. Obviously it's a different card and not the Micro SD XC kind. Other than a bit slower access speeds to the card, absolutely zero problems.... well if you don't count that it's basically filled up, hence why the 64GB option is great on the GS4. So it proves the point on the problem with the early build Micro SD XC 64GB cards.

I'm happy to see that my review has helped some others out there. Good luck to you in your warranty claim. my experience with SanDisk customer support has been excellent so far.

Update: 08/21/2013 - Received the new replacement SanDisk Storage card just a few days ago (shipping back to me once they agreed it was defective was a very short time window). Have had it running in the Galaxy S4 for a few days now without any jumps, stutters or card unloading in the middle of picture or video taking. Card seems to work flawlessly as the SanDisk Rep mentioned it would. One would think it's such a short time to test after a few days of use, but if this were not fixed already it would have dismounted in the first 45 minutes... that's how often and how fast it was occurring. so it would seem the problem is solved. The new SD card makes the phone even more responsive when moving between pictures in the gallery and performing other tasks like copying files to the card. Thanks SanDisk! Unless I update this review by next week, you will know that the problem has been fixed.

Good luck to those with similar problems as we now know how to get it fixed thanks to SanDisks great responsive customer service.

Update: 08/31/2013 - This is the last update to this review just to "close the loop". The new replacement card from SanDisk has been running flawlessly for about 2 weeks now. I have not experienced any of the initial problems. SanDisk really did fix the issues in the new batch of cards.

Update: 12/09/2013 - The card has been running in my GS4 flawlessly since replacing it around Aug 21st. Pretty good track record so far (~ 3.5 months) so it appears to be fixed with the newly manufactured (replacement) cards.

For those that have left comments that I should change the rating upwards now that the issue is fixed (see my addition at the beginning of this review)... When searching for a solution to a problem with a purchased product, most people start at the 1 star reviews to see what others have experienced. This is especially true for products with a lot of reviews (this is what I did in the beginning with this product). Therefore I think leaving it at 1 star and adding the comments at the beginning should clarify the review.

Thanks to review commenter "Da Shocker" for his input. I think he sums it up very well when it comes to the value of files stored on media like this:

"One more thing.. to those not happy with the one star rating by this person go ahead buy one. Take tons of pics vids and save some music on there then when the card crashes come back and give it a five star. A card cost $50-$100 pictures from a vacation or family event are priceless.. "
5150+ comments| 2,117 people found this helpful. Was this review helpful to you? Report abuse
 I needed a 32 GIG micro SD card to use in an Android tablet to expand the memory. This SanDisk card has such a good reputation and price that it is hard to pass up. I have used a lot of SanDisk memory cards in the past and I have never has any issues with them. I wanted a Class 10 card for the speed as I will be storing a lot of apps, videos and photos on the tablet and making sure that they were quickly transferred to the SD card and that they play with the maximum speed and quality.

I did multiple speed tests using a bench marking program to check the claimed speeds. One test was using a UBS 2.0 adapter and the other test was using a USB 3.0 adapter and both were plugged into the same computer's USB 3.0 port. I included the color graphs of the test results in my short video for your information. Using USB 2.0 I got a write speed of 16.661 MB/s and a read speed of 21.682 MB/s. I then used the USB 3.0 adapter and the same USB 3.0 port on the computer and the write speed was 19.889 MB/s and the read speed was 45.041 MB/s. That is a very good result for a Class 10 memory card.

I rated this as a 5 star item for testing so well and being sold at a great price. I also like that the card comes with a 10 year warranty. It also works perfectly in the Android tablet.
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For some devices using micro-SD cards, 32GB is the maximum size you can use. If you are considering a larger card, make sure your device can support a larger capacity. And to be safe, check that your device can handle the 32GB size as well.

My intended purpose for using this card is in my GoPro Hero 3 Black and in another sports cam I have, the Polaroid XS100 Polaroid XS100 Extreme Edition HD 1080p 16MP Waterproof Sports Action Video Camera With Full Mounting Kit Included

The SanDisk Ultra 32 MicroSDHC is a Class 10 card. A card with a high data transfer rate is a must for a sports cam such as the GoPro. Some of the issues users experience with their cameras ultimately can be blamed on a card that is too slow for the device.

I have been very pleased with the way these cards work in my GoPro. No problems whatsoever and the capacity is huge.

These are priced very reasonably and are a great value.
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on January 6, 2014
My review is a little backwards… but I thought the most relevant should go first.


The *typical* price since summer 2013 is about $24 for 32 GB, and about $48 for 64 GB. DO NOT pay any more than this, and you can actually pay less if you have the luxury of time / patience.

The lowest (non-lightning) price hit about $18.00 for 32GB and $35 for 64GB, in early December. I basically buy when the price hits $20 or less, and the 64 nears $40.00.

From December 2013 to January 2014, I watched these cards change price on an almost daily basis. They initially went on sale for about $17.95 and $34.95 for 32 and 64 respectively. I watched them slowly increase in price, with random dips and peaks for a month. On January 6th 2014, they still show as a "Best Deal on Amazon" for "7 more days" but they are at the highest price point since last summer -- and higher than I have *ever* payed for these cards! So don't let the "Best Deals" section deceive you, at $27/$50, these are NOT a "deal" in terms of price.

Okay, here's my actual "review" of these absolutely great SDXC cards.


I have tried a variety of MicroSDXC cards, and so far the Samsung Ultra UHS1 are the best -- and the price can't be beat -- for all the most important reasons: speed, capacity, reliability, durability.

I have not had a single failure, and I use these cards in my Nook HD+, Nexus 7 2013 (via USB) and my Canon 5D Mark II (with converter) and MacBook Pro (In the card slot). They're durable and waterproof, and I can use the same card in all these devices without reformatting. I even had one go through the wash, and I still use it for pictures.

For the technically inclined, I have cards with *both* the Clockwork Mod bootloader (for the Nook HD+) and the MagicLantern firmware for my Canon EOS 5D II on the same card. I can pull it from the Nook, shoot pictures with the camera, and look at the results on the Nook by just pulling the card out of one device and placing it in the other. This should be possible with any SDXC/SDHC card, but it turns out that the Samsung UHS1 is the only card I've found that works reliably. Some cards won't boot because they're too slow too finicky, but all my Samsung UHS1s work great (the 64GB will not boot in the Nook, but no 64GB card will).

I keep my eyes open for price drops on these cards because they've performed so well for me. Samsung also has a newer, faster card, but its price-point hovers somewhere north of "prohibitive" so I still stick with these. And that's good news regardless because as the new card increases its market share, these should drop even further in price.
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on June 28, 2014
I got my wife a Samsung Galaxy Tab 3 10.1 for Christmas, and it took awhile for her to start figuring out all the things it can do. Once she did, that led, of course, to her wanting to watch movies on it. That was my signal to spring into action, that is, if I wanted to prevent her from running wild, buying "digital copies" of every movie we already have in DVD or Blu-Ray. You can't play DVD or Blu-Ray movies on this device, but you CAN use your computer's DVD or Blu-Ray drive and commonplace third-party software to convert movies in this format into ".mp4" and/or several other types of video files that CAN be played on this tablet.

Since this particular tablet is capable of playing high-definition video (screen resolution is 1280 x 800 pixels), and we want to use ALL of that high-def capability, my conversion files tend to be pretty large (average 5 to 10GB per movie) ... way too big to be stored on the tablet's limited internal memory. That's where the tablet's microSD slot ... and this SanDisk flash memory ... comes in. I make HUGE mp4's, store them separately on a 1.5 terabyte drive, and then load as many of them as I can on this chip, which shows up in the tablet as a separate memory source. Then all you have to do is pull up one of the movie files from the card, and hit play. You can use the device's standard video player, or get an app with more controls.

Watching high-def video on a tablet that's streaming the data from a memory card (rather than the tablet's internal memory) requires a memory card with very high "read speed," and this SanDisk card's "Class 10" rating fills that bill. That's the difference between cheaper microSD that's primarily designed for simple data storage, and microSD that's designed for higher active transfer/read speeds. The "Class 10" designation generally means that the subject card will transfer data at a MINIMUM rate of 10MB per second. This SanDisk "Ultra" card is capable of transferring data at speeds of up to 30MB per second, depending on the speed of the device you're using it in, and other particulars of the way you're using the device.

"Frustration free packaging" means the chip, SD adapter, and plastic case comes in a little, sealed cardboard envelope with a pull tab opener. This card comes pre-formatted for Android, and my use of it in the Galaxy Tab 3 for watching high-def .mp4 movies has thus far been flawless.

Finally, don't let yourself get burned by counterfeiters in trying to save a buck. While pricing on memory tends to fluctuate, Amazon's current pricing on this card is VERY competitive with any/all vendors out there selling GENUINE SanDisk "Ultra" memory. Buy from Amazon, or other trustworthy vendor, because I just learned the hard way that these memory cards are being counterfeited in huge numbers ... that is, the counterfeiters are placing SanDisk labeling/packaging on inferior, generic microSD, and selling the bogus chips on Ebay and anywhere else they can. I bought THREE from Amazon after I got burned by a Chinese seller on Ebay. The counterfeit packaging and labeling was good enough to fool me, until I actually tried one of the chips in the Galaxy Tab 3 ... the write speed (that is, the amount of time it takes to transfer files ONTO the microSD card) was dramatically worse than the speed of a genuine SanDisk "Ultra" card, and the read speed was totally inadequate for playing movies on the Galaxy Tab 3. I may never have figured it out at all if I didn't already have one other, genuine SanDisk "Ultra" with which to compare the fakes.

If you want the best, most reliable memory for the microSD slot on your shiny, new Android device, look no further ... this is it.
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on April 24, 2013
**Update 6.24.14**
My 128 GB card stopped allowing writes via any of my card-readers on a Windows PC--either when it was inside any of several full-size SD card adapters (with the write-protect tab in either position) or plugged directly into the microSD slot of the reader. MicroSD cards have no write-protect tab, so I was quite surprised and worried by this. After failing to find any workable solution by searching online, I finally put it in my Chromebook and created a new folder on it there, then stuck it back in my Windows PC and it no longer gave me a write-protect error. If anyone has a similar problem, I'd recommend doing something similar by putting it in any other PC, laptop, camera, etc you have available and try writing to it there.

This portion of my review is necessarily being written as an update to my original review of the 64 GB version of this card, since Amazon disallows multiple reviews for what they consider the same item. This portion concerns the 128 GB version of this card:

I don't need a fast card, so the speeds on this card were not that important, besides which my test PC is not exactly high-end. Therefore I didn't count off for the speed results I got below, using a USB 2.0 card adapter, but I thought they might be relevant to some readers. While the card did reach the Class-10 and/or UHS-I requirements, it came in at under 2/3 of the claimed "read speeds up to 30 MB/s for fast file transfer." Then again, running on a second PC using a different USB 2.0 card reader, none of the speeds even hit 5 MB/s, so this seems to be highly system-dependent.

I only just got the card this week, and so far it works on *select* SDXC-compatible devices and exFAT-compatible operating systems: some SDXC-compatible devices, such as the Panasonic HDC-TM40, do not allow cards larger than 64 GB (for whatever reason); this was stated in the manual, and I've confirmed this card is recognized as broken/corrupt/unusable in that device, whereas 64 GB exFAT cards work fine. The 128 GB works fine (with original exFAT formatting) in my Toshiba Excite 7.7 Android tablet, and (predictably) not at all in my non-SDXC-compatible Galaxy Note 2 (though it possibly would if reformatted to FAT32, since a 64 GB card in FAT32 works fine there).

I'll update my review to reflect any problems, issues, etc that I notice in the coming days & weeks.

CrystalDiskMark 3.0.3 (C) 2007-2013 hiyohiyo
Crystal Dew World : [url removed as per Amazon rules]

* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]
Sequential Read : 18.694 MB/s
Sequential Write : 11.921 MB/s
Random Read 512KB : 18.502 MB/s
Random Write 512KB : 0.680 MB/s
Random Read 4KB (QD=1) : 3.339 MB/s [ 815.1 IOPS]
Random Write 4KB (QD=1) : 1.581 MB/s [ 386.1 IOPS]
Random Read 4KB (QD=32) : 3.151 MB/s [ 769.4 IOPS]
Random Write 4KB (QD=32) : 1.564 MB/s [ 381.8 IOPS]

Test : 1000 MB [G: 0.0% (0.0/119.1 GB)] (x5)
Date : 2014/04/24 16:53:49
OS : Windows XP Professional SP3 [5.1 Build 2600] (x86)

The following is my original review of the 64 GB version of this card, published April 24, 2013:

This is a high-quality card. I've used it in a variety of devices, through multiple readers on different pcs, in an HD camcorder using a micro to full-sized SD adapter, and I've never once had a problem with it. It even works at full capacity in *some* microSDHC-only devices once its reformatted to FAT32 (such as my SanDisk Clip+ FLAC player and supposedly even PSPs via a proper adapter, though I haven't yet tested my PSP). I keep anticipating someone coming out with a card with equal or better capacity and speeds at a comparable price, but I haven't seen one yet. If these were cheaper, I'd have several by now.

Make sure your device can handle micro or full-sized SDXC cards, or is one of those rare gems that state they support only as high as SDHC but have been tested to work with SDXC cards such as this one once they've been manually reformatted to FAT32.
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