http://www.newegg.com/Product/Produc...82E16820208463 8GB microsd Class 6 (speed of the card, class 6 is the highest)
http://www.newegg.com/Product/Produc...82E16820211378 class 6 16gb
http://www.newegg.com/Product/Produc...82E16820134992 16gb microsd.
I personally would get the 16, seeing as it was over 100 dollars when I bought my 8gb, and now have the 8 GB full and am constantly deleting stuff just to add new. If you listen to music and watch movies on your phone, that 8GB goes super fast.