The barrel ships with gas block. This barrel is designed for our gas block that is 1 inches long (included). A standard front sight base is 1.9 inches long and will not fit. Barrel installation should be performed by a qualified gunsmith. Installation of the gas block dowel pin and gas block is required to complete the assembly process. Features: Stainless barrel - 1:7 inches twist improved polygonal rifling with 556 Noveske Match Chamber Extended feed ramps Gas tube Pinned low profile gas block, 0.75 1/2 X 28 threads - aside from the 20 inches Medium contour