This odd thread adapter allows you to add your favorite suppressor, fake suppressor, muzzle break or other component that has a standard AR-15 thread of 1/2-28 to use on your barrel thread of thread of 5/8-24. It has female threads of 5/8x24 and outer threads of 1/2x28 ID of .358" & fits 9mm. It is composed of a steel alloy and iron-chromium-nickel steel and finished in black oxide. Call if any questions on your application. **MUZZLE BRAKE, COMP, OR SUPPRESSORS MUST HAVE SUFFICIENT INSIDE CLEARANCE FOR A .30+ CALIBER ROUND TO SAFELY USE THIS ADAPTER. USE AT YOUR OWN RISK.