These are the 11x8F Folding Propeller Blades from Advanced Precision Composites. For use on Electric powered aircraft only (not for glow engines). FEATURES: Gray composite propeller blades that assemble onto a propeller hub (hub not included, see REQUIRES). Comes in a bag attached to a header card INCLUDES: Two composite propeller blades One instruction sheet REQUIRES: 45mm prop hub and hardware for assembly, use APCQ4390. Hand and eye protection when operating propeller. ALL props require balancing (use TOPQ5700) May need prop reamer, use GPMQ5005 (SAE) or GPMQ5007 (Metric) SPECS: Diameter: 11" Pitch: 8 COMMENTS: Sailplanes have no landing gear, and therefore would break a rigid propeller when the plane came in for a landing. The folding propeller will fold back upon landing. dew 6/14/01 ir/jl