Large size 50505cm, filter mats can be cut to fit your filter for use in any aquarium or pond filter Filter mats sponges provide mechanical and biological filtration that captures large amounts of waste and is not easily clogged. Pore size is measured by the number of pores in the area (PPI), and the higher the PPI, the more pores there are 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 prefilters 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. (After unpacking, follow the instructions in the user manual, restore the size for use)