Name:tubing couplings Std Ref:API 5CT Grade:J55,K55,N80,L80,C90,P110, ... Coupling Manufacturer of Tubing and Casing coupling according to API SPEC 5CT AND 5BAPI couplings for oil tubing and ... NU, EU(tubing coupling), STC,LC,BTC(casing coupling). 5.Surface treatment: Whole phosphating, or inside phosphating and outside ... oil pumps and revolving sand gravitated device, etc API 5CT oil tubing couplings