Perfectly Compatible: Our cat water fountain filter is compatible with 3-liter round pet water fountains on the market (filter diameter: 14.6 cm), please check the size carefully before purchasing. 【Triple Filtration Protection】This cat water fountain filter is made of a layer of cotton, activated carbon, and ion exchange resin, which can filter hair, debris, and impurities, effectively eliminate odors in cat water, and ensure fresh drinking water for pets. Replace the filter regularly: We recommend replacing the filter element regularly to keep your cat's water clean. Replace your cat water fountain filter every 1 to 2 weeks in summer and every 2 to 4 weeks in winter, or more frequently if multiple animals use the water fountain. 【Note】Please soak the filter in water for 3 minutes before use and rinse thoroughly under running water to keep the product clean and the water fresh.