The VERTEX 2-stroke pistons are cast using a gravity casting process from an aluminum alloy containing 18% silicon. The silicon reduces thermal expansion at operating temperatures. This has the advantage of making the piston less prone to rattling and breaking. Additionally, silicon gives the pistons better wear properties, thus extending their lifespan. The kit includes the piston, piston rings, piston pin, and piston pin circlips! The 2-stroke piston variations include: Replica = piston conforms to the original shape, Race = performance-enhancing piston design, Pro Race = forged special piston.