Product name：UP Check valve x2
When the air pump is set below the water level, it is suggested to use check valve to prevent air pump from damage.
With this anti-backflow check valve in place, the water can never reach your pump to damage it. Save yourself the trouble of replacing the pump earlier than you need to. Extend your pump's lifetime with this check valve.
• Simple and indispensable solution for your aquarium air pump against air backflow
• Prevent water from back-siphoning into your water pump and causing water damage
• Overall Length: Approx 2.2 Eighth
• Fits 4mm air hose