OS Power backplate improves efficiency of the engine adding power and mileage using special air ports in the backplate to channel crankcase air fuel mixture.
 
Fits OS Based ( BLOK, Protek, OS, Maxima, BUllit, etc...) including the OS .28 engine as well as ALPHA RC engines  and some, NOVA and  Novarossi .21 engines with 26mm diameter backplate and 14.5mm depth.. Comes with O-Ring.
 
Please measure before you order to make sure it fits your model.
 
More POWER, more RPM and Better tuning! A must have for the serious RC racers who wants MAX power from there engine!