Used OEM Rotax front cylinder head with 31mm intake valves, 27mm exhaust valves, valve springs, valve seals, keepers, retainers and rocker arm assemblies. Part numbers for this include 420613534 420623063 420623067 We disassemble, wet blast, and clean thoroughly , this is ready to install on your engine. You may want to consider changing the valve seals although they have a very low failure rate!