CompatibilityFilters are compatible with Catit PIXI Water Fountain 2.5L (84.5 fl oz). These filters are not created or sold by Catit. Easy to UseSoak the filter in water for 5 minutes before use and rinse with running water to clear away excess carbon dust. We recommend replacing the filter every 2-4 weeks, depending on the number of cats using the fountain. Clean, Fresh WaterEach filter is made of a layer of cotton, activated carbon and an ion exchange resin to filter hair, heavy metals and improve the taste of water. Your cat will enjoy drinking clean, fresh water throughout the day. Health and HydrationBy providing your cat with clean, fresh water, you can increase their intake of water and reduce the risk of urinary tract infections.