The check valves are for common aquarium air pumps. Please DO NOT use them with CO2 system. Great one way check valve for aquarium and fish tank. Protect you air pump by preventing aquarium water from back siphoning during a power outage. Made of durable clear plastic. Net weight: 0.14 oz / 4 g. Please use a paperclip to poke it from Input side to Output side when the outlet inside gets stuck. Air Hole Diameter: 0.15" / 4mm; Overall Size: 2.1" x 0.58" / 5.3 x 1.5 cm (L*Max.D) Package Content: 6 Pcs x Air Check Valve 6 Pack Red One Way Valves The non-return air pump check valves are made of durable plastic materials and designed to fit most common aquarium air pump while making no noise. Keep your air pump from getting water running into your pump when doing water changes or when the power is interrupted. Perfect for aquariums, fish tanks and gardening etc. Note: Please don’t place the air valves in CO2 system because the high pressure will make them crack and leak. Fit standard 3/16
