... .,Ltd. produce API approved sucker rod couplings, including Class SM couplings, Class T couplings, Full size couplings and Slim Hole Couplings with the ... size range of 5/8", 3/4", 7/8", 1 ... the reliable supplier you can trust in China.API Class SM Full Size Sucker Rod Coupling 1) Material: AISI 5140 2) Standard ...