Stainless steel gas tubes are salt bath nitrocarburized for extra resistance to heat and corrosion. Nitromet finish gives added durability with a surface hardness of Rc 55. Installs easily and available for carbine and mid-length gas systems
AR-15, Issue:09, Page:012
Big Book Catalog, Issue:66, Page:012
Mil Spec 304 stainless steel, matte black Nitromet finish. Carbine- 9/34" (24cm) long. Mid-length-11 3/4" long.