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). To reduce wear, each VERTEX piston features an MOS2 coating on the piston skirt. VERTEX is the original equipment manufacturer for some of the largest motorcycle manufacturers, and many factory teams in the MXGP trust in the performance of VERTEX as well. The VERTEX Top-End Piston Kit saves time and money as this set includes everything needed for the piston replacement. Delivery includes a piston kit with cylinder gasket set and timing chain! Piston specification for 4-stroke: Pro Replica = forged piston corresponds to the original form, Pro HC = forged special piston (higher compression and performance-enhancing). Ideal for KTM and HQV motorcycles, this piston kit enhances performance and ensures durability under high-stress conditions.