Rosco Manufacturing K9 Barrel, 556NATO, 16, Intermediate Gas System, Fits AR-15, Melonite Finish, Black K9-16-HY-556-7-I The K9 16" features an intermediate length gas system with an optimized gas port to run reliably suppressed and/or unsuppressed. The K9 continuous taper is the most effective profile to dissipate heat from hard use. With weight shifted to the back of the barrel" modern attachments on the front of the rifle create a perfectly balanced and better handling rifle. Updated target crown carried over from the Purebred series. Features improved harmonics" fit and finish.