Due to the higher cylinder pressure of 4-stroke engines, VERTEX pistons are generally forged. They are crafted from high-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. VERTEX is an OEM supplier for some of the largest motorcycle manufacturers, and many factory teams in MXGP trust VERTEX's performance. The VERTEX Top-End piston kit saves you time and money as it includes everything needed for a piston replacement. The delivery includes a piston kit with a cylinder gasket set and timing chain! Piston design for 4-Strokes: Pro Replica = Forged piston conforms to original shape, Pro HC = Forged special piston (higher compression and performance-enhancing).