... the chloroprene rubber, CSM, buna-N rubber, EPDM and so on, and flange material is Q235, 304, 316 and so on. Applications : This ... prevent backflow. Obstruction-resistant, corrosion-resistant, long working life and simple installation are also the merits of duckbill valves. Aeration ... is few and the diameter is small, but the amount demand is large, is very suitable for mass production. Duckbill Check ...