... 3,Material:rubber,steel 4,12 years OEM manufacturer exper flange duckbill check valve,flexible check valve,rubber duckbill valve ... of reinforcing cord. In addition to steel pipe, the ZHW series can be easily adapted to plastic, concrete, special dimension conduits ... :Coarse bubble air diffusers Sparging nozzles 6)Applicable figure: flange duckbill check valve,flexible check valve,rubber duckbill valve