The Aqua-Mist Air Stone is a 7/16 inch green colored aerator for your tank. When added to your aquarium, it produces a steady flow of bubbles, providing a better supply of oxygen to your fish. It attaches easily to any air pump with standard 3/16’’ airline tubing (sold separately). The air stone can be positioned anywhere in your tank, either blend it in with surroundings or hide it under gravel. Use the Penn Plax Aqua-Mist Air Stone Cylinder for a beautiful aquarium and healthy fish.