This is a 5.25x6.25 Speed 400 Electric Propeller from Advanced Precision Composites. For use on electric powered aircraft only, not for glow powered engines. FEATURES: Constructed of Gray composite material For Speed 400 motor applications Two adapter rings that adapt to different motor shafts INCLUDES: 5.25x6.25 Speed 400 Electric Propeller, two adapter rings and instruction sheet REQUIRES: Assembly onto motor shaft or gear drive unit in Electric plane SPECS: Diameter: 5.25" Pitch: 6.25" Hub inner diameter: 0.24" (6mm) where rings are installed Inner Diameter of Rings: 0.188" (4.8mm) and 0.236" (6mm) tlw 9/13/07 ir/jxs