But, it's a muffler that robs a LOT of power. Besides, there aren't too many things that sound as nice as a screaming 1/2A engine. I tried one of these mufflers a while back on a Randy Randolph Bee-Tween. Needless to say, I'm removing it and going back to an APC 5.7x3. However, it was quiet enough to fly at a park with the 7x3.