... 4.Surface: black, g mild steel couplingsBS DIN ANSI Standard Carbon Steel Mild Steel Couplings screwed half couplingMaterialCarbon steel, Stainless steel, Alloy and Malleable ironStandardANSI B1 ... and DIN standard Kinds of mild steel couplings : bends, elbows ,tees, crosses, sockets, caps, backnuts, flanges, unions, nipples, bushings, plugs and so ...