VERTEX 2-stroke pistons are gravity cast from an aluminum alloy with an 18% silicon content. The silicon helps to reduce thermal expansion at operating temperatures, making the piston less susceptible to noise and fracture damage. Additionally, silicon provides the pistons with better wear characteristics, thus extending the lifespan of the piston. The piston kit includes piston ring(s), piston pin, and piston pin lock! Piston designs for 2-stroke engines: Replica = piston corresponds to the original form, Race = performance-enhancing piston design, Pro Race = forged special piston.