FeaturesWhen the oxygen pump stops working, the water in the aquarium may return to the inlet pump, causing damage to the air pump. A check valve can solve this problem. -back can prevent the air pump from entering the water and is an essential accessory. Good QualityOur check valve is made of high quality materials, which are wear-resistant and durable ,not easy to corrode and aging. The noise of the check valve is very low when used, and it will not affect your normal rest even at night. Qne-way valveOur check valves check valves are one-way valves that can effectively prevent water backflow. After the installation is completed, the check valve will slightly reduce the air outlet, but it will not affect the use Small SizeOur check valves are black and compact. Our check valve accepts a trachea with a diameter of 0.4 cm, approximately 0.2 inches. Scope 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 the air hose in sequence. Color: Black Size: 5.5 cm Quantity delivered: 10 pieces Note: The data is manual measurement, please allow 1-38cm error, due to differences between light and screen, there will be a certain difference in color, the specific received in kind shall prevail.