Given the higher cylinder pressure in 4-stroke engines, VERTEX pistons are generally manufactured from forged pieces. To withstand the internal pressure of the engine, these pistons are made from the highest 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 producers, and many factory teams in MXGP rely on VERTEX's performance. The VERTEX Top-End Piston Kit saves you time and money by including everything you need for a piston replacement. The kit comes with a piston, cylinder gasket set, and timing chain. Piston type for 4-stroke engines: Pro Replica = forged piston corresponding to the original form, Pro HC = forged special piston (higher compression and performance-enhancing).