.1-Casing Sizes: OD 4-1/2"~20" 2.Casing Grade: H40, J55, K55, N80, M65, L80, ... R3 API 5CT Casing 1.Casing Sizes: OD 4-1/2"~20" 2.Casing Grade: H40, J55, K55, N80, M65, L80 ... Casing, Tubing, Coupling. Our factory manufacture Casing, Tubing: According to API SPEC 5CT Casing . Casing Steel grade: J55, K55, ... . D. Range Tubing: From 2-3/8"to 4-1/2"(EUE/NU) Casing: From 4-1/2" to 20", Casing Threads: BTC, ...