KOSO’s replacement parts for the Grom 4V Cylinder Head is the perfect part for completing the KOSO Big Bore kit. This replacement head is great for those of you looking for a bump in power and torque, please note this kit will only fit 2014-2020 Groms with the KOSO 170cc Big Bore Kit. This kit features: a feature, stainless steel 24mm intake valves, and 20mm exhaust valves.