For Oxygen Pumps Only: Great one-way check valve for most common aquarium air pumps. NOT suitable for CO2 or other high pressure systems to avoid cracks and leaks. Small and light: size: 5.5L (cm); Diameter of air holes: 0.4 cm. Add little weight to your hose for smooth airflow. Ideal pump guards: prevent backflow of water through the tube during a power outage or break of the pump. Essential accessories for the basic aeration setup in your aquariums. Sturdy and Quiet: Made of reliable plastic that can be tightly connected to the hose without air leakage. Durable to withstand long time use without making noise. Easy maintenance: clean the valve regularly. Please push it with a thin stick from the inlet side to open it when it is obstructed inside and restrict the airflow. The red color Quantity delivered: 10 pieces