Due to the higher cylinder pressure in 4-stroke engines, pistons are generally made from forged pieces. VERTEX pistons are forged from the highest quality aluminum alloy (2618) to withstand the internal pressure of the engine. Each VERTEX piston features an MOS2 coating on the piston skirt to reduce wear. As an OEM supplier to some of the largest motorcycle manufacturers and many factory teams in MXGP trusting in VERTEX performance, you can be assured of superior quality. The piston kit includes piston ring(s), piston pin, and piston pin clip. For 4-stroke engines, the Pro Replica forged piston matches the original form, while the Pro HC forged special piston offers higher compression and increased performance.