This is the Great Planes ElectriFly 4mm to 1/4-28 / Prop Adapter with Set Screw and Propeller Nut. / / FEATURES: Large shaft size for Brushless or Brushed motors with 4mm shafts / / INCLUDES: One prop adapter / One prop washer / One 1/4-28 prop nut / / REQUIRES: Tightening the prop nut to compress the prop adapter onto the motor / shaft / / SPECS: Total length: 1.57" (40mm) / Diameter of prop washer: 1.1" (28mm) / / ajw 12-27-06 / ir/jxs