This is a .15 Ball Bearing Control Line Engine with Muffler. FEATURES: Schnuerle Porting Ball Bearing-Supported Crankshaft Steel Thrust Washer INCLUDES: One Assembled Engine w/Carb and Standard Short Glow Plug One Muffler SPECS: Bore: .590" Stroke: .550" Displacement: .15 cu in RPM (with a 8x4 prop): 14,000 Weight: 6 ozs COMMENTS: Due to an unusually small crankshaft, some brands of props will not work. I tried several brands of 8X4 props. Top Flite and APC 8x4 props WILL NOT fit. Grish, Joz, Zinger, and Master Airscrew 8x4 props fit. 11/22/92eke ir/jl