MSD's Pro-Billet Distributor with Small Diameter Black Cap and Ready to Run w/Vacuum Advance and Steel Gear, No Ignition Box needed.;CNC Machined Billet Aluminum Housing and Billet Aluminum Base; Steel Gear Installed; Polished steel shaft is QPQ coated and guided by a sealed ball bearing; Advance plate and weights are fine blanked from chrome moly steel and QPQ coated for friction reduction; Advance weight pins are staked and tig welded to the plate; Easy-to-adjust mechanical advance with supplied springs and stop bushings; Nylon pads ensure smooth operation of the advance weights; Mechanical advance assembly can be locked out for crank reluctor systems; Maintenance-free magnetic pickup and precision reluctor create stable reluctor signals throughout the rpm range;