J55, K55, N80, L80-1, P110, Q125 Material API 5CT Casing & Tubing, Seamless Casing, Well Casing, OCTG Casing, Casing coupling. For extracting oil and gas from wells.
API 5DP Drilling, For well drilling
GB9948-1988 is for manufacturing of furnace tubes, heat exchangers and pipelines in refineries