This Heavy Profile Barrel includes the Windham Weaponry Picatinny Rail Gas Block (attached to the barrel using taper pins) to which you can mount a variety of accessory front sights. Or, leave it “bare” if you intend to shoot only with a scope. Barrel material is 4150 Chrome Moly Vanadium 11595E Steel, and it is Chrome Lined in both Bore and Chamber for long wear and ease of cleaning. Button rifling is 1 turn in 9 inches – right hand twist, for optimum accuracy with a wide range of .223 / 5.56mm ammunition. A Black Manganese Phosphate finished is applied for protection against rust and corrosion. This premium barrel kit includes the Barrel Extension (with M4 Feed Ramps), Barrel Nut, Delta Ring, Weld Spring, Snap Ring, Gas Tube, Gas Tube Spring Pin, M4 Double Heatshield Handguards, Front Handguard Cap, Picatinny Rail Gas Block with Sling Swivel, Bayonet Lug and A2 Flash Hider with Crush Washer.