Due to the higher cylinder pressure of 4-stroke engines, the VERTEX piston is generally made from forged pieces. To withstand the internal pressure of the engine, the pistons are forged from the highest quality aluminum alloy (2618). Each VERTEX piston features a MOS2 coating on the piston skirt to reduce wear. VERTEX is a first fit supplier for some of the largest motorcycle manufacturers and many factory teams in the MXGP trust the performance of VERTEX. The VERTEX Top-End Piston Kit saves you time and money as this set includes everything you need for a piston change. Delivery includes piston kit with cylinder gasket set and timing chain! Piston version 4-stroke: Pro Replica = forged piston corresponding to original form, Pro HC = forged special piston (higher compression and performance enhancing).