They look exactly like the GM/Graupner pack, which I've been told is made up with Kokam cells. If it is the same then it has a 20C rating and Graupner says you can charge at 2C (10A!!!!), although I admit I chickened out of giving it that
I drove them in a B4 on carpet and the power was mental. The car came out of corners as though it had been kicked. After about 20min running hard with a 5.5 the Lipo was barely warm.
I was well impressed with it!