Universal Gas/ Oil cap is threaded 1 5/16 - 12 to fit your Moon oil tank with no modifications, but also includes a steel weld in bung for custom applications. Features a breather vent on bottom of cap to prevent gas from spitting out of the hidden vent hole. Vent can be replaced with a 10-32 set screw if no vent is desired. 100% USA made brass/aluminum construction by Lc. Fabrications. Polished finish.