Due to the higher cylinder pressure of 4-stroke engines, VERTEX pistons are generally forged. To withstand the internal pressure of the engine, these pistons are made from high-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 rely on VERTEX for its performance. The VERTEX Top-End Piston Kit saves you time and money as it includes everything needed for a piston replacement. The kit includes a piston, cylinder gasket set, and timing chain! The 4-stroke piston execution: Pro Replica = forged piston corresponds to the original form, Pro HC = forged special piston (higher compression and performance-enhancing). Experience increased durability and peak engine performance with our expertly crafted piston kits.