This is the 45mm Folding Propeller Hub for a 40mm Spinner from Advanced Precision Composites. For use on Electric powered aircraft only (not for gas engines). FEATURES: Two-piece, gray composite propeller hub that goes on each side of the folding propeller blades to hold them in place (blades are not included, see REQUIRES). Hub has molded nut insets for easy tightening. Comes in a bag attached to a header card INCLUDES: One composite propeller hub Two 3x10mm cap head screws Two 3mm nuts Two 3mm washers REQUIRES: Propeller blade sets (use APCQ4305 through APCQ4345). 2.5mm hex wrench to tighten cap head screws. Hand and eye protection when operating propeller. SPECS: Overall Length: 58mm Length between blade mounting centers: 45mm Inner mounting diameter: 8mm COMMENTS: See propeller blades for assembly instructions. Sailplanes have no landing gear, and therefore would break a rigid propeller when the plane came in for a landing. The folding propeller folds back upon landing. JAL 6/19/01 ir/jl note updt tjt 071405