Due to the higher cylinder pressure of 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). To reduce wear, every VERTEX piston features an MOS2 coating on the piston skirt. VERTEX is an original equipment manufacturer (OEM) for some of the largest motorcycle manufacturers. Many factory teams in the MXGP also trust the performance of VERTEX. The piston kit includes the piston, piston ring(s), piston pin, and piston pin retaining clips. The 4-stroke piston types include the Pro Replica, which is a forged piston corresponding to the original form, and the Pro HC, which is a forged specialty piston with higher compression and performance enhancement.