Features: 1.Made of plastic, safe, non-toxic, durable, won't change the water quality. 2.With multiple pores, makes the water change its moving direction to prolong the time for cultivating nitrifying bacteria. 3.Suitable for both freshwater and seawater, can be used with other accessories, applicable to various kinds of fish tanks. 4.Can help to create a nice living environment for water creatures. 5.Cleanable and reusable, comes with a mesh bag for cleaning the filters every 3 months. ? Specification: Features: Made of plastic, safe, non-toxic, durable, won't change the water quality. With multiple pores, makes the water change its moving direction to prolong the time for cultivating nitrifying bacteria. Suitable for both freshwater and seawater, can be used with other accessories, applicable to various kinds of fish tanks. Can help to create a nice living environment for water creatures. Cleanable and reusable, comes with a mesh bag for cleaning the filters every 3 months. Specification: Material: Plastic Color: as picture shown Capacity: 500ml / box Size: 2.2cm / 0.87inch Package list: 1 x Box of Biological Filter Media 1 x Mesh Bag