[Perfect Compatibility] Compatible with the HAPUP drinking fountain for cats and dogs. Encourage your pet to drink more water and stay healthy. [Quadruple Filtration System] Each cat fountain filter consists of a foam pre-filter and a highly porous filter layer made of cotton with high-quality activated carbon and an ion exchange resin. Cotton layer: Filters hair, sediment, and dirt. Activated carbon: Eliminates bacteria and chlorine odors. Ion exchange resin: Softens tap water and prevents urinary tract diseases. Ideal for cat health! [Improved and More Sufficient Materials] The blue and white replacement cat fountain filters are made of high-quality bulk filter material, are non-toxic, visible, easy to use, and clean. Each fountain filter material is individually packaged and well stored for optimal performance! The filter element has been completely modernized, with both quantity and quality improved to more effectively improve purification performance. [Replacement Cycle] To