Due to the increased 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 the MXGP trust the performance of VERTEX. The piston kit includes piston ring(s), piston pin, and piston pin lock! Piston type for 4-stroke: Pro Replica = forged piston corresponds to original form, Pro HC = forged special piston (higher compression and performance-enhancing). VERTEX pistons are designed to deliver peak performance under rigorous conditions, trusted by top-tier motorcycle teams for their reliability and durability. Whether you're a professional racer or an enthusiast, this piston kit ensures superior engine performance and longevity.