Yantai Yunsheng Petroleum Machine Accessories Co. Ltd., founded in 2005, is a professional manufacturer of API Spec 11B Sucker Rod Couplings, including Spray Metal coupling, class T coupling, Sub OD coupling, with various type of Full size, Slim Hole, Over Size, with Big Chamfer, with Wrench Flat, with Bidirectional Cambered Surface Protection, etc., and the thread size are available at 5/8¡±, 3/4¡±, 7/8¡±, 1¡±, 1-1/8¡±.