if you plan to use a 64gb sd card with the samsung galaxy s3(all models), then you need to find a class 4 and lower micro sd card. the class 10 cards that you find on market easily are not suited for any mobile device. tablet or phone. the class 6 and up are meant for cameras and computers. running a class 6 and up card could damage your device. so make sure you check the class rating when using an sd card.