it depends on what you're useing it for. for a 10.5 or slower 25c or 30c is what all the guys at my track are running. for 8.5 or faster 15c or 20c is sufficiant. for eighth scale electric i'd assume you want a lot of power and a good amount of run time so 20-30c with 4000+ mah should be good. i could be wrong on the eighth scale but it sounds right considering you want speed and time. oh yea i'm not pos. but you might want to try a 3s 11.1v lipo for eighth scale although i'm looking at the orion 3200 3s 11.1v for my 2wd not sure but it might be good.