Large size 50×50×4cm, the filter mats can be cut to fit your filter for use in any aquarium or pond filter The filter mats Sponges provide mechanical and biological filtration that capture large amounts of waste and are not easily clogged. Pore size is measured by the number of pores in area (PPI), and the higher the PPI, the more pores in the (fine) sponge. It is recommended to use a combination of sponges of different specifications for best results. Safe for aquatic animals and free of dyes. Filter mats are commonly used as pre-filters for wet/dry filters, collection tanks and reservoir filters. Regular cleaning, reusable after cleaning, durable Compression packaging vacuum sealed, easy to store, does not take up space, suitable for all types of aquariums.