1、Built in ceramic rings for obstruct a lot of particles in the water, filter cotton(white cotton) for adsorbed residual impurity, biochemical cotton(black cotton) for remove odor and purify water. 2、The air holes are interchangeable, so it is easy to culture nitrifying bacteria, filter water impurities and decompose fish excrement. 3、Special air chamber can generate a lot of tiny bubbles, increase oxygen capacity, no noise. 4、Can be matched with air pump(The pump is not included). 5、Suitable for using in fish tank and aquarium. Features: 1. Built in ceramic rings for obstruct a lot of particles in the water, filter cotton(white cotton) for adsorbed residual impurity, biochemical cotton(black cotton) for remove odor and purify water. 2. The air holes are interchangeable, so it is easy to culture nitrifying bacteria, filter water impurities and decompose fish excrement. 3. Special air chamber can generate a lot of tiny bubbles, increase oxygen capacity, no noise. 4. Can be matched with air pump(The pump is not included). 5. Suitable for using in fish tank and aquarium. Specification: Condition:100% Brand New Material: Acrylic Color: As Pictures Shown Size: approx.7*7*12.5cm/2.8*2.8*4.9in Package list: 1 * Aquarium Filter