Uxcell Aquarium Non-Return Air Pump Check Valves 2 PCS Non-Return Check Valves for Aquarium Air Pump They are made of plastic material for long time use The Aquarium Valves are important accessories for air pumps Measuring approx. 2.08" long, 0.56" diameter; Tip outside diameter: 0.18" Package Included: 2 x Check Valves