I honestly have no idea. But, I wouldn't be surprised if they have exclusive rights to their own cells, so that no other vendor can get a hold of them. After all, they do have some pretty oddball cell capacities (relative to other brands).

I have one of the electric power 6600mah (7.4volt)packs for my xxx-t. I dont have a way to test the "c" rating but it has worked fine for me for over a year now. I have just decided to change packs recently to cut a little weight for racing though.