... 4,12 years OEM manafacturer experience Duckbill Valve,adjustable check valve,rubber duckbill valve1: Product Introduction 1:Rubber check valve is made of rubber ,it ... looks like a duckbill and is a new draining valve with functions of forward inflow and reverse back ... sizes we also can supply to you 5:certificates obtained: Duckbill Valve,adjustable check valve,rubber duckbill valve