nut and bolt Hexagon Nuts with black,zinc ,HDG Standard: DIN934(555, 936), ... alloy steel Platings: black oxide, zinc, chrome, galvanized, nickel, dacromet, delta-tone, geomet and ruspert Grade: 4, 6, 8 and 10Standard ... ) Material: Carbon steel Diameter: 5-20mm. HYFJ-006 nut and bolt