Feature: 1. When the air pump is placed below the water surface, the valve prevents water from damaging the front air pump or other product equipment. 2. Export pump with check valve, it will immediately turn off to avoid the risk of water backflow when the air pump is powered off and stops working. 3. Suitable for 4mm/0.2in diameter tubes, can mend or extend standard air line hose. 4. Unique plunger design, provides reliable, tight shut off, compact and convenient. 5. Manufactured from premium plastic material, durable and sturdy, can effectively prevent water from entering the air pump. Specification: Conditon: 100% Brand New Item Type: Air Pump Check Valve Material: Plastic Color: BlueProduct Length(Single): Approx. 3.5cm/1.4in Suitable for: Inlet/outlet pressure tube with approx. 4mm/0.16in diameter Function: Used to reverse the water flow caused by the pressure difference between the inside and outside when the oxygen pump suddenly stops working, to prevent the damage to the oxygenation pump and the overflow of the water in the cylinder to form property damage. . Package List: 10 x Air Pump Check Valve