Due to the higher cylinder pressure of 4-stroke engines, VERTEX pistons are generally made from forged billets. To withstand the internal pressure of the engine, the pistons are forged from the highest quality aluminum alloy (2618). To reduce wear, every VERTEX piston features a MOS2 coating on the piston skirt. VERTEX is an OEM supplier for some of the largest motorcycle manufacturers, and many factory teams in the MXGP trust the performance of VERTEX. With the VERTEX Top-End Piston Kit, you save time and money as this set includes everything needed for a piston replacement. Delivery includes: Piston kit with cylinder gasket set and timing chain! Piston variant 4-stroke: Pro Replica = forged piston corresponds to the original shape, Pro HC = forged special piston (higher compression and performance-enhancing)