Welcome to ShenMo shop! Medium bubbles: The air stone disc produces dense and abundant bubbles. A great way to increase oxygen solubility in your aquarium and enliven aquatic life. Model: ASD-040; Spray volume: 2 L/min; Recommended air pump power: 2W - 4W; Standard Air Tube ID: 0.5cm. Suitable for use in aquariums, fish tanks and small ponds. Reliable Material: Made of mineral material and sintered at high temperature. Ideal for aeration in a DWC tank. Helps maintain healthy fish or root growth. Stable in Water: Each disc measures 4D(cm) and weighs 28.3g. Its round, flat shape allows it to always sink to the bottom and sit securely in the tank. Easy to use: Soak the stone completely in water for 1 hour before use. Clean it regularly with a brush because it clogs after weeks or months of use. Due to manual measurement, the products you receive may have some dimensional errors Due to different monitors, the products you receive may be slightly different from the pictures Actual delivery quantity: 4 piece 100% satisfaction - Our customers are our priority. If you find any problems with the products after receiving the goods, such as damage and incorrect quantity, please contact us immediately. We do our best to provide you with satisfactory after-sales service.