The VERTEX 2-Stroke Pistons are gravity cast from an aluminum alloy containing 18% silicon. The inclusion of silicon reduces thermal expansion at operating temperatures, which makes the pistons less prone to chatter and fracture damage. Additionally, silicon enhances the wear properties of the pistons, thereby extending their lifespan. The piston kit comes complete with piston ring(s), piston pin, and piston pin retainer! 2-Stroke Piston Variants: Replica = Piston matches the original form, Race = performance-enhancing piston design, Pro Race = forged special piston.