Introducing the Brownell’s Retro A1 carbine length barrel assembly. Chambered in 5.56x45, the chrome lined barrel has a 1-12 twist and finished in black phosphate with an overall length of 16”. Muzzle threads are ½-28 and features a standard rifle barrel extension. The assembly includes a front sight base, .625 No F Marks, sight post, detent, spring, sling swivel, rivet, flat delta ring, barrel nut, weld spring, snap ring, and round handguard cap. Machined from 4150 chrome moly steel. Everything you need for your Retro barrels!