Different springs and stop bushings are supplied so you can tune an advance curve to match your application. Must be used with an MSD 6, 7 or 8-series ignition. MSD Pro-Billet Distributors are the finest performance and racing distributors available. Every feature has been engineered to endure the rigors of high performance and racing engines. Whether cruising the streets or racing stock cars, dragsters, boats or trucks, MSD has a distributor for it. MSD uses state-of-the-art, Computer Numerical Controlled (CNC) mills and lathes to machine each housing. After a long series of precise cuts and movements, the billet is formed into a flawless distributor housing that is accurate to within 0.001". The flex-free housings are lightweight, have no porosity or weak areas and look great on polished, show quality engines.