Specification:Condition: 100% Brand NewItem Type: Non-Return Check ValveMaterial: plasticColor: As picture shownOptional Size: 3mm, 5mm, 7mm3mm: The interface diameter is 3mm/0.1in5mm: The interface diameter is 5mm/0.2in7mm: The interface diameter is 7mm/0.3in Suitable for: Aquarium air pumpFunction: Used as an oxygenation pump due to the water current reversed due to the pressure difference between the inside and outside when it suddenly stops working, damages the oxygenation pump and causes the water in the tank to overflow to form property damage, prevents the water in the fish tank from flowing back into the air pump, and burns the air pump to avoid danger. Indispensable accessories for air pumps.Package List:10 x Non-Return Check Valve