Pawfly 10 Pack Aquarium Non-Return Check Valves;

Place in your airline tubing between your air pump and aquarium water to prevent water returning down the airline.

How to clean
Unscrew and open up check valve, pinch the rubber boot inside valve to make sure small slit is open. Otherwise no air to tank.

Be attention:
Please DO NOT use them with CO2 system.

Made of durable clear plastic. Package Weight: 38g/1.34oz