This is a Scale Retractable Tailwheel Assembly for .45-.75 Scale Aircraft. FEATURES: Operates from a Retract Servo or Air Cylinders. Self-Centering Steering. Self-Locking Down. INCLUDES: One Assembled Tailwheel Retract Unit REQUIRES: One Tailwheel For Pneumatics, use ROBQ2365 Air Cylinder COMMENTS: The retracting mechanism on this will need an area in the fuselage with these dimensions: Height: 3", Length: 2", Width: 1.5" ir/jl