Cotton net: filter any deposits that may exist in tap water and carefully capture hair, sediment and debris. Eco-friendly cat fountain filter: 4 pieces/pack , replace the filter every 2-4 weeks to maintain water freshness. For pet health: Help filter drinking water, let our pets drink from it. water safely and stay healthy. Notes: Pay attention to measure the filter cotton size of the water dispenser before purchase, as shown in the figure. < p>PET Water Dispenser Filter: The activated carbon in the filter can remove bad taste and odor, keeping the water clean and fresh.