Non-toxic mineral material: air stones are made of high-quality non-toxic mineral material and sintered at high temperature, and the stones are strong and durable. Dimensions of Airstone: Each disc measures 4 cm D x 1.5 cm H. Suitable for use in aquariums, aquariums and small ponds. Due to its round and flat shape, it can always sink to the bottom and lie stably in the tank. Recommended air pump capacity: 2 W - 4 W; Standard ID aviation hose: 0.5 cm. Supplying oxygen: connect it to the air pump and place it in the water so that the air pump can pump oxygen into the water. Ideal for adding oxygen to ponds, hydroponics and circulation systems and reducing the CO2 content. Wide application: these air stones can be used in aquariums, ponds, aquariums, freshwater, saltwater aquariums, hydroponics or and aqua farms. The small and dense bubbles produced by air stones can not only provide oxygen for fish, but also create beautiful and fairy-tale bubble scenes under water. Great gift idea: Air Stones provide oxygen for fish and are the best gift for aquatic animal lovers.