DN
The card seemed to work well in most devices that I tried it in, but in a Samsung Galaxy S4 it would continue to unmount and mount over & over on the phone - a known issue on the Galaxy S4 forums due to a possibly bad batch of them.  I tried to reformat the card in the phone and from a PC computer, but that didn't help.  Finally I just called SanDisk and they had to RMA the card, which took about 2 weeks from start to finish when I had the new card in my hand.  The new 64 GB card from SanDisk looks slightly different, but still has gray & red on it.  However, it now works great in the Galaxy S4 and hasn't had any unmounting issues now for the past 3 weeks.Good card for pretty much everything else, except in the new Samsung Galaxy S4 phones.