Medium Bubbles: Air stone balls produce dense, abundant bubbles. A great way to increase oxygen solubility in your aquarium and enliven aquatic life. Jet Volume: 5L/min; Recommended air pump power: > 4W; Standard ID Air Hose: 0.5cm or 0.9cm. Well constructed and efficient for long time service. Reliable Material: Made of mineral material and sintered at high temperature. Ideal for aeration in aquariums, DWC systems or ponds. Keep fish or roots healthy Stable in water: Each ball is 5cm in diameter and weighs 106g. Well weighted to sink to the bottom and sit stably in your tank for steady bubbles. Easy to use: Soak stone completely in water for 1 hour before use. Clean it regularly with a brush because it clogs after weeks or months of use.