Size:7mm Quantity:1 batteries required:No Item Weight:31 g Specification: Condition: 100% Brand NewItem Type: Non-Return Check ValveMaterial: plasticColor: As picture shownOptional Size: 3mm, 5mm, 7mm3mm: The interface diameter is 3mm/0.1in 5mm: The interface diameter is 5mm/0.2in 7mm: The interface diameter is 7mm/0.3in Suitable for: Aquarium air pump Function: 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 About this item Prevent the water in the fish tank from flowing back into the air pump and burn the air pump to avoid danger. Protect you air pump by preventing aquarium water from back siphoning during a power outage. The check valves are for common aquarium air pumps. Please DO NOT use them with CO2 system. Great one way check valve for aquarium and fish tank. We greatly value our customers and want you to be completely satisfied with your purchase. If you aren't happy with your shopping experience or product, we urge you to contact us so we can resolve the issue When the position of the air pump is lower than the water surface, prevent the backflow of water from damaging the front air pump or other equipment. After adding the check valve, the air pump can be placed above the water surface or below the water surface, and there will be no backflow of water when the air pump stops working. Using plastic material, beautiful and durable. 3 different sizes for you to choose, meet your different needs.gifts for christmas See more product details Prevent the water in the fish tank from flowing back into the air pump and burn the air pump to avoid danger. Protect you air pump by preventing aquarium water from back siphoning during a power outage. The check valves are for common aquarium air pumps. Please DO NOT use them with CO2 system. Great one way check valve for aquarium and fish tank. We greatly value our customers and want you to be completely satisfied with your purchase. If you aren't happy with your shopping experience or product, we urge you to contact us so we can resolve the issue When the position of the air pump is lower than the water surface, prevent the backflow of water from damaging the front air pump or other equipment. After adding the check valve, the air pump can be placed above the water surface or below the water surface, and there will be no backflow of water when the air pump stops working. Using plastic material, beautiful and durable. 3 different sizes for you to choose, meet your different needs.gifts for christmas