This ultra slim thread adapter allows you to add your favorite suppressor, fake suppressor, muzzle break or other component that has a standard AR-10 thread of 5/8-24 to your AR-15 thread of 1/2-28. It has inner threads of 1/2-28 and outer threads of 5/8-24. It is composed of a steel alloy and iron-chromium-nickel steel and finished in black oxide. Call if any questions on your application. Thread Protector sold separately.