Name:tubing coupling Std Ref:API 5CT and 5B Grade:J55,K55,N80,L80,C90,P110 ... 4-1/2 Threads:NU, EU Coupling Manufacturer of Tubing and Casing coupling according to API SPEC 5CT AND 5BAPI couplings for ... -3/8" 4.Type: NU, EU(tubing coupling), STC,LC,BTC(casing coupling). 5.Surface treatment: Whole phosphating, or inside ... of oil pumps and revolving sand gravitated device, etc. API 5CT tubing coupling