VERTEX 2-stroke pistons are gravity cast from an aluminum alloy containing 18% silicone. The silicone content reduces thermal expansion at operating temperatures, which has the advantage of making the piston less susceptible to rattling and fracture damage. Additionally, silicone provides better wear characteristics to the pistons, thereby extending their lifespan. The piston kit includes the piston, piston ring(s), piston pin, and piston pin clips. Piston Types for 2-Stroke Engines: Replica = piston corresponds to the original shape, Race = performance-enhancing piston type, Pro Race = forged special piston.