Ballistic Advantage Premium Series 16″ SPR 6mm ARC Barrel, Mid Length. Manufactured from 416R Stainless steel with a bead blasted finish, this 6mm ARC caliber barrel is perfect to finish your latest AR-15 workshop project. This Premium Series barrel features a 16″ length, a 1:7 twist rate, 5/8 x 24″ TPI, and a .750″ Mid-Length gas system. Offering premium statistics for a competition or show-off build as well as providing quality operating performance from your rifle, this barrel will keep you ahead of the competition. Features: 16″ Length 416R Stainless Steel SPR Profile