The air check valve can prevent the aquarium from backflow water, which is caused by the decrease, and keep the function and service life of the carbon dioxide cylinder. When used in the ozone generator, air check valve can prevent the ozone from backflowing to the air pump and the erosion of the propeller. Aquarium check valve can protect the power head from backflow water which is caused by power failure. Simple check valve is easy to install, requires no additional tools and can be attached to any place you want in seconds. These stainless steel One Way Check Valves are suitable for CO2 supply system in fish tank, aquarium and others.