This is the 55mm Folding Propeller Hub for a 45mm 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 cardINCLUDES: One composite propeller hub Two 3x10mm cap head screws Two 3mm nuts Two 3mm washersREQUIRES: Propeller blade sets (use APCQ4305 through APCQ4360) 2.5mm hex wrench (GPMR8012) to tighten cap head screws Hand and eye protection when operating propellerSPECS: Overall Length: 63mm Length between blade mounting centers: 50mm Inner mounting diameter: 8mmCOMMENTS: 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. The use of this hub will shorten the overall diameter of the prop by 10mm from the manufacturer"s length listing.NOTE: Currently we do not carry collets or prop shaft adapters to fit this pro- duct. Please contact APC.APCPart APCLPFH4