The Mission First E- VolV Low Profile Gas Block (1” Length) was designed for use with the AR15, M4 and M16. 1 inches long, constructed out of steel with a Manganese phosphate finish. Fits .750 barrels and mounts utilizing the included knurled cup pin steel set screws. Allows usage with handguard systems that extend past the standard gas port location on the barrel. Made in the USA, with a Lifetime Warranty.• Fits .750 barrels• Steel with a Manganese phosphate finish• Mounts utilizing knurled cup pin steel set screws