Specification: Type: Sponge Filter Material: Sponge Color: Sky Blue Inner Diameter: 3/4 cm Outer diameter: 9/10.8/10 cm Length: 7.3/10.2/20cm REGULAR CARTRIDGE REPLACEMENT: Changing your Paper filter cartridge is part of the routine maintenance of your pool and regular cartridge replacement can be costly. These washable and reusable foam filters will reduce your costs. SAVE YOUR MONEY AND TIME: Replacing the filter element with paper is part of daily pool maintenance. Replacing a conventional filter element can be very expensive. These washable and reusable foam filters will save your costs. KEEP WATER CLEAN: The filter cartridge sponge is recommended to replace one carton per week, it will keep your pool, jet massage water of clean and fresh pure spa, the foam filter will work about 2 months. It applies to most massage pools, with this filter, you can enjoy the safe and healthy massage pool spa. 3 SIZES: S: the length of the pool filter is 7.3cm, inner diameter: 4cm, outer diameter: 10.8cm. M: The length of the pool filter is 10.2cm, Inner diameter: 3cm, Outer diameter: 9cm. L: the length of the pool filter is 20cm, inner diameter: 4cm, outer diameter: 10cm, the filter is suitable for S type filter, which will meet your needs. WIDE USAGE: The filter cartridge sponge is suitable for filter pumps using the H-type cartridge, suitable for swimming pool, spas, baths, aquariums, etc.