Key Features 3 Pack of 13mm x 25mm Cylinder Airstones High quality durable and non toxic mineral materials making them safe for use around fish Produces small even air bubbles that provide essential oxygen and aeration in Aquariums Can be used in Aquariums and small ponds. Takes a 4mm Airline tubing with a 2.5w Recommended Air Pump Washable and reusable. Regular cleaning with a brush is recommended to clean off any clogged up debris Water rich in oxygen is essential for happy, healthy fish and plants in your aquarium. Furthermore combined with the right pump, the generated air bubbles can act as an impressive display feature. Air stones require a pump and airline to get the air to them, these are both available separately in our store.