The sera PrefiX Filter allows enhancing the filter volume of a connected filter by up to 1.6 liters (0.4 US gal.) with two variably useable filter baskets. The motorless filter is, for instance suitable as a prefilter in case of cloudiness, as a quick filter in case of pollution or as a biofilter for expanding the filter capacity of small external filters. The sera PrefiX filter can be connected to a pump or an external filter by means of a sera hose 16/22 mm. Connecting several PrefiX filter in series is also possible. In case of fine grained filter media, using filter net bag is recommended.sera PrefiX Filter -Universal Filter-+ Pre, bio or quick filter+ without pump, has to be integrated in an existing filter circuit or powered by a separate pump+ filter volume: 1.6 l+ 2 filter baskets+ connectors with taps for hose size 16/22+ for freshwater and marine water+ dimensions: height: 31.5 cm, diameter: 13 cm