Fits YZ 125 years 2005-2009 and takes capacity to 144cc. Aluminum cylinder with nickel-carbide coating ported to "FACTORY" specifications. Bud racing head, 100% CNC machined with removeable bronze dome allowing higher compression and anti-detonating features. Holds more water volume for increased cooling. Specially designed high performance hard anodized power valves (will not fit stock cylinder). Specially designed high performance cast light flat top piston. Performance gasket kit, including required seals and hardware.