Duckbill check valve common material main three types.

1) Silicone valve (FDA food grade and medical grade)

2) LSR & Liquid silicone rubber valve (FDA food grade and medical grade)

3) Rubber valve  (NR: Natural rubber, NBR: Nitrile Butadiene Rubber, HNBR: Hydrogenated nitrile rubber, SBR: Styrene Butadiene Rubber, CR: Neoprene Chloroprene Rubber, IIR : Isobutylene Isoprene Rubber, EPDM: Ethylene Propylene Diene Monomer, FKM: Fluororubber , Viton, FVMQ )