The VERTEX 2-stroke pistons are manufactured using gravity casting from an aluminum alloy with an 18% silicon content. Silicon reduces thermal expansion at operating temperature, which means the piston is less prone to rattling and breakage. Additionally, silicon gives the pistons superior wear characteristics, thus extending the lifespan of the piston. The piston kit includes piston ring(s), piston pin, and piston pin circlip! Piston Variants for 2-Stroke Engines: Replica = piston conforms to the original shape, Race = performance-enhancing piston design, Pro Race = forged special piston.