The Bravo Company (BCM) low-profile gas block sits under a free-float rail on AR-15/M4 builds with a .750" barrel journal. The bore is honed to spec for proper gas alignment. Features: .750" journal, honed to spec Machined steel with phosphate finish Low-profile height clears free-float rails Includes two 10-32 knurled set screws Gas tube is not included. Fits .750" barrel journals only - not .625" or .875".