... effect is.4, Corrosion protection,aging protection,no deformation,high adaption and long service life5, Wide size,norminal size ... Drainages in sewers11: Submerged outfall diffuser nozzles6:Drainage from sewage reservoirs12:Coarse bubble air diffusersSparging nozzles3)Dimension4)application figure5 ... ,duckbill valve,slip on duckbill check valve For Sewage Treatment slip on Flexible Rubber Duckbill Valve