This is a 7x4E Thin Propeller from Advanced Precision Composites. For use on electric powered aircraft only (not for glow engines). FEATURES: Gray composite construction Comes with two adapter rings that adapt to different motor shafts INCLUDES: One 7x4E Thin Electric Propeller with two Adapter Rings REQUIRES: ALL props require balancing, this is VERY important, use TOPQ5700. May need prop reamer, use GPMQ5005 (SAE) or GPMQ5007 (Metric) SPECS: Diameter: 7" Pitch: 4 Hub inner diameter: 0.25" (6.3mm) jxs 11/22/11 ir/jxs