Proco Products, Inc. is the global leader in the design and supply of expansion joints and rubber duckbill check valves for piping systems. The Series 700 ProFlex® rubber duckbill check valves are commonly used in the water and sewage industry. Check valves are a cost-effective way to control back pressures from sewage treatment plants, outfalls, and tidal operations. NSF/ANSI 61 Standard certification is available on the Rubber EPDM Expansion Joints and ProFlex™ Rubber Check Valve products.