The Breek Arms Plan B Echo is a single-port muzzle brake for 5.56 NATO / .223 barrels threaded 1/2x28. It redirects propellant gas to counter recoil and muzzle rise, so your sights settle back on target faster for flatter follow-up shots. 1/2x28 is the standard thread pitch on most 5.56 AR-15 barrels. The single-port layout keeps the brake simple and compact on the end of the barrel. Features: Single-port muzzle brake design Sized for 5.56 NATO / .223 bores 1/2x28 threads Reduces felt recoil and muzzle climb Before you install: confirm your barrel is 5.56/.223 and threaded 1/2x28. Do not mount a 5.56 brake on a larger-bore barrel. Use a crush washer or shims to time the port correctly, and check bore alignment before firing. Muzzle brakes are loud, and much of the blast is directed to the sides. Wear hearing protection and be mindful of anyone on the line next to you.