This gas block replaces your existing front sight to provide a simple, low profile design that can be used to mount a rifle length forearm to a carbine length barrel. The clamp style is mounted by the use of two clamping screws. The set screw style clamp is mounted with a set screw. Specs: Compatibility: 0.750" Barrels Material: 4140 Chromoly Steel Finish: Mag phosphate Weight: 1.8 oz. Width: 0.90" Height: 1.48" Includes: (1) gas block with (2) screws Note: Gas tube roll pin is not included. Roll pin included with all of our gas tubes. Mfg: Phase 5 Tactical