Name:tubing coupling Std Ref:API 5CT and 5B Grade:J55,K55,N80, ... by customer's request 3.Size: tubing coupling from 1.9" to 4-1/2",Casing coupling fro4-1/2"to 13-3 ... /8" 4.Type: NU, EU(tubing coupling), STC,LC,BTC(casing coupling). 5.Surface treatment: Whole phosphating, or inside phosphating ... oil pumps and revolving sand gravitated device, etc. API 5CT tubing coupling