This is a 10x6E Thin Composite propeller from Advanced Precision Composites For use on Electric powered aircraft FEATURES: Gray composite propeller blades that assemble onto a propeller hub. Comes with five adapter rings that fit into propeller hub to allow for different motor shaft diameters. INCLUDES: One composite propeller Five composite adapter rings Instruction sheet REQUIRES: All props require balancing. The Top Flite Power Point Propeller Balancer (TOPQ5700) can be used for this purpose. If prop reamer needed, use GPMQ5005 (SAE) or GPMQ5007 (Metric). SPECS: Diameter: 10" (250mm) Pitch: 6 Hub inner diameter: 0.25" (6.4mm) Adapter sizes: 3.3mm (1/8"), 4mm (5/32"), 4.9mm (3/16"), 6.0mm (1/4"), 8.0mm (5/16") COMMENTS: This propeller should not be used on gas or glow engines.