Feature:1. Made of high quality PVC material, sturdy, durable and long service life.2. When the position of the pump is lower than the of the water, to prevent water backflow damage to the front end of the pump or other product equipment, after the addition of stop valve pump can be higher than the of the water or lower than the of the water placed.3. There is no danger of water backflow when the pump is cut off and stopped working, it is the small guard of the gas supply facility.4. Using pump is very easy to handle and use to prevent water from entering the machine pump.5. Used as an oxygenation pump due to the pressure difference between the interior and outside when it suddenly stops working, which causes the water to reverse, damage the oxygenation pump and cause the water in the cylinder to overflow to form a property loss. Prevent the water in the fish tank from flowing back into the pump, burn the pump to avoid danger, it is an indispensable accessory of the pump.Specification:Condition: 100% Brand NewItem Type: Check ValveMaterial: PVCColor: As Picture ShownQuantity: 20PCSWeight: Approx. 43gSingle Length: Approx. 4.4cm/1.73inchSuitable: Inlet/Outlet Pressure Gage Pipe: Approx. 4mm/0.16inchPackage List:20 x Check ValveNote:Each outlet needs to be connected, and the double-headed pump needs two stop valves, and so on. It is recommended to buy to prevent the water in the hose of the oxygenation pump from flowing back to the machine and damaging the front-end pump or other product equipment during power outages.Using tips:1. The use of stop valve will slightly reduce the amount of gas, because there is resistance, but the impact is not large.2. If you receive the stop valve and find that there is no outlet after connecting i