... , CLASS B, CLASS CSurfaceHot Dipped Galvanized, Electro Galvanized, Natural finished, Chemical blackThreadsDIN, BS, NPT, Metric, BSPT, BSP, NPS (ISO7/1, DIN ... , water ,oil and electricity connection etc. Materials: carbon steel ,stainless steel ,alloy steel . Surface of mild steel couplings: cold galvanizing,hot galvanizing,and black Egdes: banded ...