Supercharger Drive hub for X-6 and X-10 crank drives, multiple options available:
Aluminum w/ keyed 7/8" bore (ProCharger F-1 & F-2)
Aluminum w/ keyed 1" bore (Centrifugal Specialties R-series, ProCharger F-3)
Steel, splined (Centrifugal Specialties R-series, ProCharger F-3 & F-4)