Due to the higher cylinder pressure of 4-stroke engines, pistons are generally made from forged components. To withstand the internal pressure of the engine, VERTEX pistons are forged from the highest quality aluminum alloy (2618). To reduce wear, every VERTEX piston features a MOS2 coating on the piston skirt. VERTEX is the original equipment manufacturer (OEM) for some of the largest motorcycle manufacturers, and many factory teams trust VERTEX's performance in the MXGP. The kit includes a piston, piston ring(s), piston pin, and piston pin clip! Piston version for 4-stroke: Pro Replica = forged piston corresponds to original form, Pro HC = forged special piston (higher compression and performance-enhancing). This kit ensures durability and reliability for high-performance 4-stroke engines. The high-quality materials and advanced manufacturing process make it a preferred choice for professional racers and motorcycle enthusiasts alike. By opting for the VERTEX Pro Replica, you ensure that your engine operates at its peak performance, enduring high pressures with minimal wear and tear.