... J55, K55, N80, L80,P110 2.Thread: BTC,STC,LTC 3.Standard: API 4.Place of Origin ... : China 13 3/8" btc casing coupling -----------------------------------------------------------------------------------------------------------FeaturesGRADE: J55, K55, N80-1, N80 ... TYPE: NUE, EUE (tubing coupling), STC, LC, BTC (casing coupling).SURFACE TREATMENT: Whole phosphating, or inside ...