Coupling ,sub-coupling ,polished rod coupling are designed in accordance with API SPEC 11B and made of fine ...    More ...

Coupling ,sub-coupling ,polished rod coupling are designed  in accordance with API SPEC 11B and made of fine carbon-steel or alloy steel(equivalent  to AISI 1526 or AISI 4135).
Normally, they have two wrenches one the outside diameter but they also can be providing in no wrench when required by user.
 Standard of  API Spec 11 b and SY/T5029-2006 , main specifications: 5/8/3/4 (SM), 3/4/7/8 T (SM), 7/8/1 T (SM), 1/11/8 T (SM) also can be customized according to user requirements
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