i use a 8gb sandisk class 2 and i cant fault it. the only time iv reformatted it was when i was using the ultamario theme on my ak2i the theme wudnt let my acekard load up, so i had to delete the theme after the format. and i have a spare 4gb kingston class 4 the only difrence is when i move data from my laptop to the sd card it writes over faster at like 16 mbs or something like that while my sandisk class 2 to writes the data over at 8 mbs, but i cant tell the difrence when its in my acekard not that iv noticed