Product Line: MSD. Part Type: Module Selector. Part #: 8672. The user can then select between twelve different rpm limits by simply turning the knob. Holley, Holley EFI, Aeroflow, Aeromotive, B&M, MSD, Brawler, Hooker, Hurst, Mr Gasket, MSD Dynaforce, NOS, Quick Fuel Technology, Racepak, Spal Fans, Weiand, Jesel, Wilson Manifolds, Competition Cams, Crower Lifters, Johnson Lifters, Daimond Pistons, CP Pistons, CP Carrillo, RCD, GRP, Dailey Engineering, Manton Pushrods.