Triple Filtration for Healing Water Guard One: High Intensity Cotton When resting on the floor, hair, dust, and other small impurities can easily fall into the fountain. With high intensity cotton, our fountain filter effectively filters out hair, debris, and sediment. Guard Two: Activated Coconut Carbon Made from natural coconut shell carbon, it reduces residual chlorine and other contaminants. It helps purify drinking water and improves taste, encouraging pets to drink more. Guard Three: Ion Exchange Resin Unfiltered tap water contains calcium and magnesium ions that may contribute to mineral buildup in pets. The ion exchange resin helps remove heavy metal ions, softens water, and supports urinary tract health. Please measure the dimensions before purchase. Outside diameter: 125 mm Inner diameter: 37 mm Generally fits 2.0-2.5L cat water fountains, such as Aerb, DAYPET, Parner, Toozey, and especially PewinGo cat fountains. [NOTICE] Not compatible with CATIT Water Fountains. Rinse before use. Rinse the fountain filter for 10 minutes before first use to remove loose particles from the coconut carbon and prevent them from entering the water. Flat side up. For optimal filtration, place the filter with the flat side facing up. Replace the filter every 2 to 4 weeks to maintain the best filtration performance. (In dusty environments or homes with multiple pets, more frequent replacement is recommended.) Individually packaged. Each filter comes in its own plastic packaging for easy storage and freshness. Help ensure clean, fresh water for your pets. Note: Measurements are manually taken. Please allow 1–3 cm variation. Due to differences in lighting and screen display, colors may vary slightly. Actual product may differ slightly from images. Delivery Quantity: As shown in the main image.