... "4.Type: NU, EU(tubing coupling), STC,LC,BTC(casing coupling). 5.Surface treatment: Whole phosphating, or inside phosphating ... or by requirements of customers Our company manufacture and sell casing and tubing couplings,pup joints, tool joints, adapter pup ... adapter couplings, stabilizers, air-liquid separators, anchors of oil pumps and revolving sand gravitated device, etc. Tubing and Casing Couplings