Please DO NOT use them with CO2 system. The one way check valves are for common aquarium air pumps.
Protect you air pump by preventing aquarium water from back siphoning during a power outage.
Made of durable clear plastic. Net weight: 4g
Air Hole Diameter: 4mm/ 0.15"; Overall Size: 5.3 x 1.5cm/ 2.1" x 0.58"(L*Max.D)
Package Content: 10Pcs x Air Check Valve.