[Perfect compatibility] Compatible with the HAPUP water fountain for cats and dogs. Encourage Your Pet to Drink More Water and Stay Healthy. [Triple Filtration System] Each cat water fountain filter is made of high-density porous filter cotton layer, activated carbon high quality and ion exchange resin. Cotton layer: filters hair, sediment and debris. Activated carbon: eliminates bacteria and chlorine odors. Ion exchange resin: softens tap water and helps prevent urinary tract diseases. It can keep the cat's drinking water clean and fresh. [Premium Quality Safe]Replacement cat water fountain filters are made of high quality material, non-toxic, visible, easy to use and clean. Plus, black and white design makes it easy to know when to clean and change filters. The filter provides cleaner water for your pet and reduces the risk of illness. [Replacement Cycle] To help prevent charcoal dust from escaping, please rinse the fountain filter thoroughly cat under running water before use, and soak it for ten minutes (a little activated carbon powder is normal), providing clean water for cats and dogs. Clean the HAPUP cat fountain filter weekly. We recommend replacing the filter every four weeks to keep the water clean. [Good Deal and Friendly Service] It's a good deal to have these 6 pet fountain filters , which can ensure long-term use.