I bought this for my Samsung galaxy s4. I don't know if it is my phone or the card but my phone says it was unexpectedly removed from time to time. My wife's phone doesn't do it as often but still does it. Very fast but unreliable. I have had many sandisk before and this is the only one I have had problems with. I have read that there were some that were poorly made. Thinking I will send it back and give it another chance.