This item is an airstone which is sintered at high temperature. With the delicate surface and even air outlet, it can be used to transport oxygen to the fishes and other living things not only in fish tank, but in pond and aquarium and other places. Besides, it can also used in purification, filtration and water ozone sterilization and aeration. Features - Color: As shown in the picture. - Material: Sand. - Size: 4.8 * 1.5 * 1.5cm/ 1.9 * 0.59 * 0.59 inch (L*W*H). - Easy to use: Connect to the air pump and put it into the water, helping the air pump to pump oxygen into the water. - and hard material, good for long-term use and safe for living things. - Can be washed repeatedly. - Beautiful air bubbles add beautiful scenery to the aquarium and fish tank.