... and Sino-SouthKorea Joint Venture Henan Changmao Yuanyi Valve Co.,Ltd , we specialize in the enquipment ... absorber, pipe damper, seal, gate valve,check valve, foot valve, filters, valves, pressure balance valve, valve, butterfly valve, pipe expansion joints, bellows, waterproof ... and technology cooperation to advance improvement!Rubber Back Valve,appearance of duck bill shape , whole rubber structure ...