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; Jet 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 x 1.8H (cm) and weighs 28.3g. Its round, flat shape allows it to always sink to the bottom and sit securely in the reservoir. 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.