... the manufacture and export of sucker rod coupling, including SM full size coupling, SM slim hole coupling, T full size coupling, T ... are made according to the API Spec 11B. The class SM Sucker Rod Coupling is my special product, which is processed ... (AISI 5140)2) Standard: API Spec 11B 3) Class: T& SM , Sub Coupling4) Main specification: 5/8", 3/4", 7/8 ...