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: 5.4L x 1.4W (cm); Air holes diameter: 0.3cm; Weight: 3g. Standard air tube ID: 0.5cm. Add little weight to your hose for smooth airflow. Ideal Pump Protectors: Prevent backflow of water through the tube during a power outage or pump break. 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.