... : API 4.Place of Origin: China 13 3/8" btc casing coupling -----------------------------------------------------------------------------------------------------------FeaturesGRADE: J55, K55, N80-1, N80-Q, L80, C90, P110We ... 4-1/2” to 13-3/8”TYPE: NUE, EUE (tubing coupling), STC, LC, BTC (casing coupling).SURFACE TREATMENT: Whole phosphating, or inside ...