The coupling is a tool with internal thread to connect the tubing or casing themselves with external thread. We can supply the coupling with external diameter from 63.5mm to 431.8mm according to API SPEC 5CT. The coupling thread types are STC, LTC, BTC, etc. And we also provide OEM service. The annual production capacity is more than 1 million pieces. Please contact email@example.com for a quotation.