This valve has a mouth shape similar to the bill of the duck, People call them silicone duckbill check valve, rubber duckbill check valve, also named duckbill check valve, check valve, on way valve, not return valve etc. They can be made of silicone or rubber material ( Flurosilcione, NR, NBR, HNBR, SBR,  Neoprene CR, IIR, EPDM, FKM, FVMQ ). It has a elastic line slit on one side to control the direction of air or fluid function. Silicone rubber duckbill Check valve are are widely used in medical device, health care, automotive, home appliance, water handle, aquarium, feeding Pets food process equipment etc.