Works like a charm with smart phones, and especially the older "flip" type - no longer do I have to search for a charging spot - it is small enough to carry in a belt pouch and works fast - during lunch or whatever.
I like this item. I am consistently draining my phone or in a place where I do not have access to power my phone from the car or power cord. The power pack is a god send and allows me to carry extra power around in the small 1/2 X 3 in device. I love it and recommend it for those always on the go.
I bought this because the price is right and to compare with the other quality batteries I have. So far, so good, but for the under $6 Amazon Prime sale price don't expect much. The unit I have says "Designed in Calif. by E-filiate" which may or may not mean much as I'm not familiar with them, but it does say "RoHS compliant." Make sure you don't have a cheaper clone. A quality standalone 18650 battery such as from Orbtronic or Voidhawk or Nitecore will cost you about $20 apiece, although the cheaper ones from Efest and AW are still said to be decent for less money. The problem is that cheap power banks like this one likely have second tier quality 18650 batteries that failed quality control. The manufacturer doesn't want to put their own name brand on them so they sell them to other companies who buy them in bulk for pennies on the dollar. Put in a small circuit board and aluminum or plastic case, charge $15 for it, and watch the money roll in. Will update my review if it performs better than expected. But the number of 1-star vs. 5-star review here pretty much tells it all. As I write this there are 45 1-star and 42 5-star reviews. So caveat emptor.
My uncle had a small square red charger so I was looking for something compariable. I found this and could not be happier. It is small a little bigger then a lipstick. Does have some wieght to it so does ass to the purse. But not too bad. and after a Day at disenyland, Texting, taking and sending pictures on the iphone 5 I was able to re charge from 30% to 100% and then 30 % to about 70% was when I last looked at it but then got in the car and used that charger. The only thing I worry about is losing the Charging cable!