I use this card in Smasung Galaxy S4 active and before that I used it in my Samsung Galaxy Note 2. It has always worked flawlessly and never given me a single problem. I use the card to copy movies to it. Playback is always smooth. I mostly play high definition movie rips. These require a lot of processing power and data transfer from the card. It has always done great. I will continue to buy this card. I have one in my MacBook Air for backups. Again, no problems.- Damon