I haven't figured out yet if I'm a dummy or if I have a defective card.  I don't know if the card is bad since I can't even get the card to stay in my Samsung Galaxy S4.8.  The little card will go in (the larger one won't) but it won't stay in.  If I put pressure on it the Samsung says .. preparing SD card but as soon as I release pressure the Samsung says .... card removed.This card came from a source outside of Amazon and took way to long to get here.  It arrived in a white envelope with NO instructions.  I'm very upset about this purchase as I've never had a problem before with either SanDisk or Amazon.  I'll try to find someone with more experience than me to give this a try before I return it.  I would have expected this to come in a package from SanDisk, like other SanDisk products I've bought in big box stores or from Amazon but it did not.