... : black, g mild steel couplingsBS DIN ANSI Standard Carbon Steel Mild Steel Couplings screwed half couplingMaterialCarbon steel, Stainless ... couplings : bends, elbows ,tees, crosses, sockets, caps, backnuts, flanges, unions, nipples, bushings, plugs and so on. Carried Standard: ... gas, water ,oil and electricity connection etc. Materials: carbon steel ,stainless steel ,alloy steel . Surface of mild ...