Due to the higher cylinder pressure in 4-stroke engines, pistons are generally made from forged parts. 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 MXGP trust in the performance of VERTEX. The piston kit includes a piston, piston ring(s), piston pin, and piston pin circlip! 4-stroke piston version: Pro Replica = forged piston matching the original form, Pro HC = forged special piston (higher compression and performance-enhancing). VERTEX's commitment to quality and performance makes these pistons a top choice for serious riders and racers. The high-quality materials and precise engineering ensure durability and enhanced engine performance, providing a reliable option for both casual riders and competitive racers.