Ballistic Advantage Premium Series, SPR Profile Barrel, 6MM ARC, Fits AR15, 18 Threaded Barrel, 5/8x24 Thread Pitch, 1:7 Barrel Twist, Mid-Length Gas System, Bead Blasted Stainless Steel Finish, Silver BABL6MM002P This 18" 6MM ARC barrel is machined from 416 Stainless Steel with a bead blasted finish. The Premium Series Barrels feature a Nickel Boron Coated Extended M4 Feed Ramp Extension.