Add a little attitude to your Cummins billet valve cover! These fill caps are designed to work with our billet Cummins valve covers, HOWEVER, THEY WILL ALSO WORK ON A FACTORY 03+ COVER !! We have taken actual 44 Mag casings and pressed them into a billet CNC machined fill cap! Key Features: - They are designed to work with our valve covers ONLY** Compatible with: 44 Mag Billet Oil Fill Cap (05-17), Cummins, Engine & Engine Parts