The Rosco K9 Barrel offers a proprietary patrol length gas system that is smoother than a carbine length, more reliable than a mid-length. Because this is the optimal amount of gas, the barrel runs reliable suppressed and/or unsuppressed. The K9 continuous taper profile is a proven profile from the past and the best to dissipate the heat from hard use. Updated target crown carried over from the Purebred series. Features no 90 degree cuts, improved harmonics and fit and finish. Note: Comes with patrol length gas tube