[Perfectly compatible] with HAPUP water fountains for cats and dogs. Encourage your pet to drink more water and stay healthy. [Quadruple filtration system] Each cat water filter is made up of a separator foam pre-filter, a high density porous cotton filter layer, high quality activated carbon and ion exchange resin. Cotton layer: filters out hair, sediment and debris. Activated carbon: eliminates bacteria and the smell of chlorine. Ion exchange resin: softens tap water and helps prevent urinary tract diseases. Ideal for your cat's health! [Improved and more adequate material] The blue and white cat water fountain replacement filters are made from high quality, non-toxic, visible, easy to use and clean bulk filter material. The filter material for each fountain is stored in individual packages and is well preserved for optimal results! The filter cartridges have been completely upgraded with improved quantity and quality for more effective cleaning. [Replacement interval] To prevent charcoal powder from escaping, rinse the Blue & White Cat fountain filter thoroughly under running water and soak for 10 minutes before use. Clean the Blue & White HAPUP Cat Fountain Filter weekly. We recommend changing the filter every four weeks to keep the water clean. Please place the flat end facing upwards to ensure optimum filtration! [Good deal and friendly service] Owning these 6 blue and white pet fountain filters is great value for money and will guarantee long term use. If you have any problems with your cat's water fountain carbon filter , please feel free to contact us."