... Spec 11B standard ,inclding class SM coupling,class T coupling,Sub coupling,Full size, Slim hole and Over Size.Main Couplings listNameSizeGradeCharactersRemarksSucker Rod ... 1-1/8”T, SM Including the following SM Coupling, T Coupling, and Sub Coupling SM Coupling5/8”; 3/4”;7/8”; 1”1 ... but also the rod,preventing and slowing down the wear.The coupling has many types and sizes ,and it is made of good ...