Tubing & Casing Coupling Coupling is the joining of two short length pipes by the means of male and female threads. All types of couplings have internal threads which are known as female thread forms. These thread forms are usually machined so that they can be coupled with the external threads on pipes known as male thread forms. Couplings are strictly designed as per API specifications. There are two types of tubing couplings widely used in the pipeline coupling manufacturing industries namely: Non-upset Thread Tubing Coupling External-upset Thread Tubing Coupling Oil Pipes Keywords: API 5CT Steel Pipe, J55, K55, L80, N80Q, C90, T95, P110 Oil Pipe, Tubing, Petroleum Casing Pipe, OCTG 1) Size: O.D. 1.900", 2-3/8", 2-7/8", 3-1/2", 4-1/2" 2) Grade: J55, N80, L80, C90, T95, P110 3) Wall thickness: 3.18 - 10.54mm 4) Length: R1, R2, R3 5) Thread: 8RD and 10RD 6) All our Tubing are designed and manufactured according to API SPEC 5CT standard