... ISO14001 2,DN25mm~5000mm 3,Material:rubber,steel 4,12 years OEM manafacturer experience Rubber Duckbill Valve,flexible check ... size,norminal size:DN50~DN1200mm3:Rubber Check Valve Application Scope Applicable Scope:1:Sewage systems7: Stormwater outfall2:Drainage systems8: Flood control ... Duckbill Valve,flexible check valve,rubber check valve 12 years manufacturer Flexible Rubber Duckbill Valve