The PETNF Replacement Filters are designed to help keep your cat’s water clean and fresh. These filters are made of high-quality materials that are easy to clean and maintain. The PETNF Replacement Filters are available in a set of six that are individually packaged and sealed to maintain high quality. These filters are designed to trap hair and debris before it reaches the water pump of the cat fountain. They are also recommended to be replaced every two to four weeks to keep the water fresh and clean.