Speed-Pro developed powerforged pistons and set the pace in powerforged technology. The high silicon VMS-75 alloy is found exclusively in pistons "powerforged" by Speed-Pro. Up to 3,000 tons of force forges aluminum slugs into the basic piston form which creates a grain flow pattern in the structure providing excellent strength, ductility and improved heat dissipation. Please Note: All compression ratios are figured with a gasket thickness representative of those commonly used and are approximate.