This '74 style muzzle brake is threaded to M15x0.75LH to fit the factory threads on the 410 shotgun barrels. They are marked "U.S.A." or "Made In USA" and count as a compliance part. They are designed to work with all loads from slugs to shot.

If you do not intend to use my S410 Front Sight Block with indexing pin, you may want to pick up one of my Crush Washers or Muzzle Nuts to index the brake properly. I also have Thread Protectors available as well.