Perfectly Compatible: Our cat fountain filter is compatible with the round 3-liter drinking fountains available on the market (filter diameter: 14.6 cm). Please check the size carefully before purchasing. Triple Filter Protection: This cat fountain filter is made of a layer of cotton, activated carbon, and ion exchange resin, which can filter hair, dirt, and impurities, effectively remove odors from cat water, and ensure healthy 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's fountain filter every 1-2 weeks in summer and every 2-4 weeks in winter, or more frequently if multiple pets use the fountain. 【Note】 Soak the filter in water for 3 minutes before use and rinse it thoroughly under running water to keep the product clean and the water fresh.