Yantai Yunsheng Petroleum Machine Accessories Co., Ltd, founded in 1997, is a professional manufacturer of API 11B sucker rod couplings, including Spray Metal coupling, class T coupling, Altra High Strength,Sub OD coupling, with various spec. of Full size, Slim Hole, grand chamfer, Two-way camber, etc. With world top level equipments and technicians, the monthly production capacity is more than 30,000pcs. All of our products are excellent in quality and low in price, which satisfied many of our customers home and overseas. Recently years, we invest over 13,000 square meters in area and USD1.5 million planning to produce API 11B sucker rod. We are API 11B Certificate Approval Company, Golden supplier of Alibaba.com and the best supplier you can trust in China.