MSD 8577 Pro-Billet Distributor Billet housing is 5/8 inch and has a smaller diameter than stock Ford distributors Easy-to-adjust mechanical advance with supplied springs and stop bushings Maintenance-free magnetic pickup and precision reluctor create stable trigger signals throughout the RPM range Polished steel shaft is QPQ coated and guided by two sealed ball bearings Advance plate and weights are fine blanked from chromoly steel and QPQ coated for friction reduction