This is the Great Planes ElectriFly 8.0mm to 3/8-24 Prop Adapter with Set Screw and Propeller Nut. FEATURES: Mounts onto the shaft coming out of the gearbox or motor with the included set screw. The propeller mounts onto this with the included nut. Aluminum prop drive Metal hardware One year quality guarantee. Compatible with any electric flight motor with a 8mm diameter shaft INCLUDES: One Replacement Prop Drive One 5/64"X4mm Set Screw One 9/16 (14mm) Propeller Nut REQUIRES: Installation onto the motor or gearbox shaft. SPECS: Length: 1.86" (47.29mm) end to end 1.09" (27.6mm) complete shaft w/.96" (24.4mm) threaded portion. Diameter: 3/8" (9.5mm) prop shaft .31" (8mm) ID for motor shaft 1.4" (35mm) largest part of hub (thrust washer portion) .62" (15.8mm) smallest part of hub