The filter element of the cat water dispenser adopts high-density PP cotton, activated carbon, and ion exchange resin triple filtration. Which can effectively filter micro-particles such as sediment and metal, purify water, filter harmful substances in the water, and provide pure water for cats. The filter can catch hair and debris, filter heavy metals, and improve water quality. Every piece is individually packaged and sealed to maintain high quality. Replace the filter monthly or more often if you have multiple cats. One box of filters will last you about 6-9 months for multi cat homes and 12 months for single cat homes. Compatible with most fountains. Filter Diameter: 5 in Inner Diameter: 1.5 in