I have a REX XRP528R (.28,8port) and it's sick! Talk about power! It would flip my Savage off the ground and backwards on it's lid so violently, that it would bounce back onto it's tires, about 90% of the time. Running an 18t pinion,a 49t spur, w/ Losi LST tires, top speed was about 50mph! It would wheelie shifting into 2nd gear!