The internal tf card that comes with the tablet seems to be either class 2 or class 4. The consensus seems to be that a class 4, and probably even the class 2 is perfectly adequate for the job it has to do, there was a post about a class 10 card actually being slower than the original class 2/4 card because of poor random write speeds. My feelings are that if I want to watch a film, which I would normally do from the external tf card I would put it on a faster card because there would not be many random writes involved in watching a film, I want the playback to stutter free, and the price difference between a class 4 and a class 10 is negligible......Win - win!