... COUPLING, JOINING SUCKER ROD, GRADE SM,T&SUB, API SPEC 11B, SIZE1-1/8" 1", 7/8", ... 3/4", 5/8", API APPROVAL PRODUCER Yantai Yunsheng Petroleum Machinery Parts Co., Ltd ... coupling ,which are all in accordance with API SPEC 11B standards for production, selling both at ... , but also by friction, abrasion resistance, extended collar and tubing life. 2) Materials: Materials international 40Cr ...