Description: Quality Material: This Aquarium Air Check Valve is made of quality PP material, ensuring a tight fit without leaking, not easy to break and can be reused Protect Your Air Pump: Specially designed air check valve protects your air pump by preventing aquarium water from backflowing during power outages Function: Place these fish tank air pump check valves in air line between the air pump and aquarium water to prevent water from backflowing along air line Applicable Scope: 3 Way Non Return Valves Pump Protectors fit standard aquarium air pipe with an inner diameter of approximately 4 mm Easy to install: The Non Return Check Valve is easy to install, easy to use, removable, and anti falling, which can effectively prevent water from backflowing and damaging the air pump Size Chart: 36x51mm/1.42x2.01inch Package Includes: 4pcs 3 way Aquarium Check Valves Note: Please allow slightly errors due to manual measurement and different monitors.