VERTEX 2-stroke pistons are cast using a gravity casting process from an aluminum alloy with 18% silicon content. The silicon reduces thermal expansion at operating temperature, which means the piston is less susceptible to rattling and fractures. Additionally, silicon improves wear characteristics, thereby extending the piston life. The piston kit includes piston ring(s), piston pin, and piston pin lock! Piston types for 2-stroke: Replica = piston corresponds to the original form, Race = performance-enhancing piston design, Pro Race = forged special piston.