Given the higher cylinder pressure in 4-stroke engines, pistons are generally made from forged pieces. To withstand the internal pressure of the engine, VERTEX pistons are forged from the highest quality aluminum alloy (2618). Each VERTEX piston features a MOS2 coating on the piston skirt to reduce wear. VERTEX is an original equipment manufacturer for some of the largest motorcycle manufacturers, and many factory teams in the MXGP rely on the performance of VERTEX. The piston kit includes piston ring(s), piston pin, and piston pin circlip! 4-stroke piston types: Pro Replica = forged piston matches original form, Pro HC = forged special piston (higher compression and performance-enhancing). The VERTEX Pro Replica Piston Kit is specifically designed to deliver superior performance and durability. The advanced MOS2 coating significantly reduces friction, resulting in longer lifespan and better response in high-pressure environments. Trusted by top motocross teams, this kit is your optimal choice for delivering peak performance and reliability in your Yamaha engine.