Our company produced coupling including sucker rod coupling,sub-coupling and spray coupling, they are design according to API Spec 11 B standard.Using the high quality carbon steel or alloy steel (the equivalent of AISI 1045 and AISI 4135) and plating metal is a kind of surface hardening technology, is the nickel, chromium, boron and silicon powder coated on the substrate metal and fused with the laser processing, after the process, the metal surface makes harder,density higher and more uniform, the friction coefficient is very low and the corrosion resistance is very high. Slim hole (SH) diameter and standard size (FS) of conventional sucker rod and polished rod have plating metal (SM) .Under normal circumstances, there is two wrench on the coupling and the outside circle, but according to user we can also provide no wrench square.Hardness of coupling T is HRA56-62 after heat treatment, with good corrosion resistance and wear resistance, when using sucker rod coupling,is connecting with the same size rod, sub-coupling is used for connecting to difference size of the sucker rod or connect the polished rod and rod string .Coupling type: Class T (full size and slim hole ) ,Class SM (full size and slim hole ).