Please DO NOT use them with the CO2 system. One-way check valves are for common aquarium air pumps. Protect your air pump by preventing aquarium water from siphoning back during a power outage. The detachable design makes it easy to clean and repair. Unscrew to open. Air hole diameter: 4mm, overall size: 4.3 x 1.5cm (L*D), net weight: 4g. Package content : 6pcs x air check valve.
