Feature: Mini fish tank filter. Filtration: can filter water and help to culture nitrifying bacteria. Aeration: instead of air buble, achieve the purpose of increasing oxygen. Usage: connected to the outlet hole of air pump and used directly in the fish tank This small filter is very suitable for 40cm / 15.7in length or small fish tank. Specification: Size: 75x75x100mm/75x75x120mm Material: environment friendly plastic Color: random