look, even class 10 works, but j3 just does not write at that speed on the card....it will not make anything better, and is a LOT more expensive.... is like buying a 10 feet cable (400$) even throught you could have bought a 2 feet (100$) for a pair of sennheiser hd800(1200$), even throught the cable makes no difference to the sound, and your amplifier is on the table, so the cable will stay on the floor.....