... .9-4-1/2 Threads:NU, EU Coupling Manufacturer of Tubing and Casing coupling according to API SPEC 5CT AND 5BAPI couplings ... 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 ...