SureFire muzzle brakes are individually inspected for concentricity and alignment, and each is covered by SureFire’s No-Hassle Guarantee. Fits: M4, M16 and variants wih 1/2-28 muzzle threads. Mounts: All SureFire SOCOM Series 5.56mm/.223 caliber sound suppressors. Note: SureFire SOCOM Series Fast-Attach sound suppressors and current-model muzzle brake/suppressor adapters and flash hider/suppressor adapters are not compatible with previous SureFire Fast-Attach sound suppressors, muzzle brakes, or flash hiders. For complete and current information on this item please see the manufacturer's website.