... ,C90,N80-1,N80-Q 4.Type: NU,EU Coupling manufacturer of Tubing and Casing coupling according to API 5CT AND 5B ... Size:tubing coupling from 1.9"to 4-12",casing coupling from 4-1/2" to 13-3/8"4.Type:NU, ... EU(tubing coupling),STC,LC,BTC( ... casing coupling)5.Surface treatment: whole phosphating, or ...