Tower says .25-.32 for a 2-stroke.

REQUIRES: Electric Motor: 8.4V 680 size with 3.1:1 ratio gearbox, spinner and
propeller, Now available MPUA3668
Speed Control: Electronic, if using electric motor
Battery: 8.4V, NiMH recommended
OR Engine: .25 -.36 cu in (4.1 - 5.9 cc) 2-stroke
OR .26 - .30 cu in (4.1 - 4.9 cc) 4-stroke
Muffler: Sports-style, engine mounts in a 90° position
Radio: 4 channel
Servos: Three mini size, 1-Aileron, 1-Elevator, 1-Rudder (1-Throttle
if glow engine is used)
Misc. Items: Building and field equipment


Regards,
Curtis