Strike Industries's black coated gas tube is the ideal upgrade to match a standard or custom AR build. The matte finish gives off no reflection, and the black oxide coating process is in accordance to Military Spec MIL C 13924. The roll pin is slightly over sized to accommodate most gas blocks and can be modified to fit smaller gas blocks.The gas tube is a basic part of a working AR and Strike Industries is manufacturing all four major gas tube lengths - Pistol 6-3/4 inches, Carbine 9-3/4 inches, Mid 11-3/4 inches, and Rifle 15-1/8 inches. These polished stainless steel gas tubes are exactly what you need for replacing an old worn tube or installing onto a new rifle. Each roll pin is slightly over-sized to accommodate most gas blocks and can be modified to fit smaller gas blocks. The SI-Gas tube is made from a high quality, corrosion resistant, stainless steel construction. Mil-correct dimensions ensure positive fit and function in a wide range of different builds. Each roll pin is slightly oversized for increased retention. Features: Mil spec stainless steel 304 Over sized roll pin included