These pistons are made from forged 4032 alloy that has an 11% silicon content. Pistons are formed in a forging press an then fully machined. the combination of this alloy and forging process allows the piston to flex under detonation or pre-ignition, giving the best resistance to cracking. Since 4032 alloy has a low expansion rate but higher than the Keith Black Hypereutectic pistons, it will require a .001" wider piston to wall clearance. Keith Black forged alloy pistons are suited for High Performance street and race applications including high compression and NOS equipped bikes. All pistons come with a set of Hastings piston rings, piston pins and spiral piston lock rings.