Rosco Manufacturing K9 Barrel, Continuous Profile, 5.56 NATO, 16″ Threaded Barrel, 1/2X28 Thread Pitch, 1:7 Barrel Twist, 416R Stainless Steel, Intermediate-Length Gas System, Fits AR15, Nitride Finish, Black, Includes Intermediate-Length Gas Tube K9-16-HY-556-7-I