The Cornerstone thread insert muzzle brake is a 17-4PH stainless steel insert for use with the Sportsman Direct Thread silencer.The 1/2x28 Insert can be used on small calibers up to 300WM. Sportsman Direct Thread Silencers come with a 5/8x24 TPI muzzle brake thread insert and installation tool.The Sportsman Taper Mount Thread Insert should not be used as a standalone brake.