... E Name : tubing couplingsCoupling manufacturer of Tubing and Casing coupling according to API 5CT AND 5B API couplings ... for oil tubing and casing Size and SpecificationsDescriptions and size Type of TreadO. ... coupling from 1.9"to 4-1/2",casing coupling from 4-1/2" to 13-3 ... 4.Type:NU,EU(tubing coupling),STC,LC,BTC(casing coupling)5.Surface treatment: whole phosphating, or inside ...