My Droid Razr runs a little slow, is it because of this card?  I can't be sure.  What I am sure about is I put this card into my GoPro Hero 3 Black Edition and the video I record comes out choppy.  So I bought the SanDisk Extreme Pro 16GB version of this card, and the GoPro works fine now.  SanDisk is normally very good, so perhaps I somehow got a bad Ultra card.  I never returned or exchanged it because the warranty had expired before I tried it in my GoPro and knew for sure the card was slow.  The SanDisk Ultra should work in the GoPro Hero 3 according to the GoPro website, so again, perhaps I just got a subpar card...