10 Pieces Black Silicone Duckbill Valve One-Way Check Valve 25.5 x 17 x 24.5 MM for Liquid and Gas Backflow Prevent: Amazon.com: Industrial & Scientific
Rubber – CASTFLOW VALVES
Rubber Check Valves
Perlick Rubber Check Valve for Sankey Beer Coupler
Check valve - Fits all keg couplers - Premium quality - buy here
10 Pieces Black Silicone Duckbill Valve One-Way Cross Check Valve 15 x 8 x 14 MM for Liquid and Gas Backflow Prevent: Amazon.com: Industrial & Scientific
Replacement Rubber Check Valve for US Sankey Coupler
10 Pieces White Silicone Duckbill Valve One-Way Check Valve 15 x 9.2 x 12.8MM for Liquid and Gas Backflow Prevent: Amazon.com: Industrial & Scientific
EZ-FLO Rubber Check Valve in the Water Pump Accessories department at Lowes.com
Island Water World | Duckbill Check Valve Kit Rubber Black 1 1/2"
Enbar rubber check valve 20.5x8 - Hortispares
Flood-Guard 4 In. Rubber Float Gasket Check Valve - Parker's Building Supply
Titan Flow Control CV 41-DI Ductile Iron Dual Disc Wafer Type Check Valve w/ Nitrile Rubber Seat & SS Disc - ANSI Class 150 - John M. Ellsworth Co. Inc.