This is an APC 50mm Folding Electric Hub For 45mm Spinner. This two-piece, gray composite propeller hub goes on each side of the APC folding propeller blades to hold them in place.
The 50mm Folding Propeller Hub can be used with a 45mm spinner or similar. For electric powered aircraft only (not for gas engines). This hub has molded nut insets for easy tightening and includes hardware.
Overall Length: 63mm
Length between Blade Mounting Centers: 50mm
Inner Mounting Diameter: 8mm ID with 30 deg. taper for collets