FeaturesWhen the oxygen pump stops working, the aquarium water can flow back to the inlet pump, causing damage to the air pump. A non-return valve can solve this problem.; The check valve can prevent the air pump from entering the water and is an essential accessory. Good QualityOur check valve is made of high quality materials, wear-resistant and durable, not easy to corrode and age. The noise of the check valve is very low when in use and will not affect your normal rest, even at night.; Qne-way valveOur check valves are one-way valves that can effectively prevent water from flowing back. Once installed, the check valve will slightly reduce the air output, but this will not affect the normal operation of the air pump. Small sizeOur check valves are black and compact. Our check valve accepts a trachea with a diameter of 0.4 cm, or about 0.2 inch. ApplicationOur check valves can be used as air pump accessories for aquariums and fish tanks. The check valve is easy to install, just connect the air pump and air hose in sequence.