I second the Webra 50 GT. If you are in the quest of saving weight this engine has the highest power to weight ratio in its class. The engine weights around 13 1/2 ounces with muffler attached!!!!! This engine is a real powerhouse not giving up any ground to the OS .50 or the Irvine 53. Its transitions extremely fast on the throttle too. I have this engine on my TopCap ARF using a 12x4 APC and it is a rocket out of a hover. I had to put the battery and the reciever as far foward as I could in the wing to acheve my CG at 5". It flys very well here do all the 3D style manuvers well. The harrier and elevator are very smooth using spoilerons at 50% and elevators drop straight down when the spoileron is used. Mixing the flaps to the elevator during waterfalls makes the plane waterfall within its on length. Very cool eye opening manuever from a 10 foot hover. 2 degrees of right thrust makes torque rolling easy.