The VERTEX Top-End Piston Kit for KTM, HQV, and GASGAS Pro HC is designed to withstand the higher cylinder pressures found in 4-stroke engines. VERTEX pistons are typically forged from high-quality aluminum alloy (2618) to endure the internal pressures of the engine. Each VERTEX piston features a MOS2 coating on the piston skirt to reduce wear and tear. VERTEX is an original equipment manufacturer for some of the largest motorcycle manufacturers, and many professional MXGP teams trust in the performance of VERTEX pistons. The VERTEX Top-End Piston Kit saves you time and money by including everything you need for a piston replacement: piston kit, cylinder gasket set, and timing chain. Piston type for 4-stroke: Pro Replica = forged piston adheres to original form, Pro HC = forged specialty piston (higher compression and performance boosting), Note: Comp 13.5:1, EXC(F), FE, EC(F).