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Does Not Protect All Cards (With Video Proof - See Comments)
on September 24, 2011
I bought two of these sleeves and in basic home testing, they did not block a reader from reading the information on cards inside them. I created this short video showing the lack of blocking, including a test using simple tin foil around the card for comparison.
UPDATE 9/28: Thanks to the prompt response from the seller and some research, we have determined that the protection depends on the type of passive RFID card. Though the specific information on the frequency range these sleeves by Stronghold are designed to cover is protected by patent (see comments), they do not work with the lower frequency 125kHz cards, which are used by access cards, animal tracking and product authorization, according to a quick search. So I guess it takes a bit of research to tell if the sleeve will block the kind of card you want to protect or not (I got mine to block access cards, which it doesn't do).