... .Place of Origin: China 13 3/8" btc casing coupling -----------------------------------------------------------------------------------------------------------FeaturesGRADE: J55, K55, N80-1, N80-Q, ... -1/2”, Casing coupling from 4-1/2” to 13-3/8”TYPE: NUE, EUE (tubing coupling), STC, LC, ... BTC (casing coupling).SURFACE TREATMENT: Whole phosphating, or ...