Zeroyoyo 1.6'' X 0.3'' One Way Stainless Steel Check Valve For Aquarium Co2 System / Air Pump (Silver Color) Material:Stainless steel ; Color:As the picture shown; Size: 4 cm x 0.8cm / 1.6'' x 0.3'' Suitable for CO2 supplying system in fish tank, aquarium and others. It can prevent the aquarium from water flowing back, which is caused by the decrease, and keep the function and service life of Carbon dioxide bottle. When used in the Ozone generator, it can prevent the Ozone from flowing back to the air pump and eroding the propeller. It can protect the power head from the water flowing back which is caused by power cut.