Fortis Manufacturing, Inc. Billet Magazine Catch, Nitride Finish, Olive Drab Green, Magazine Catch Only AR15-MC-6061-ODG The Fortis Billet Mag Catch is a superior alternative to the ones found in a mil-spec lower parts kit. Easily installs in seconds and instantly upgrades your rifle. This upgrade is CNC machined from a solid piece of 6061-T6 aircraft grade aluminum or 303 Stainless Steel Black Nitride Coated or Case Hardened.