This is the Great Planes ElectriFly 8mm Prop Adapter Motor Shaft Collet 3/8-24 Output Shaft. FEATURES: Fits standard size propellers onto a 8mm motor shaft Large shaft size for motors with 8mm shafts INCLUDES: One prop adapter One prop washer One 3/8 prop nut REQUIRES: Tightening the prop nut to compress the prop adapter onto the motor shaft. SPECS: Total length: 1.88" (47.8mm) Diameter of drive washer and prop washer: 1.1" (28mm) rmb 12-02-06 ir/jxs