Features: Cotton layer, activated-carbon and ions exchange resin forming a three-layer filtration system. They can filter hair, particle, heavy metals, and improve the tastes of the water so that pet can drink clean water from cat fountain. Please soak the filter in water for 2 minutes and rinse it thoroughly under running water before use and change the filter every 3-4 weeks. The filter is your pet fountain necessary accessory. Own it, and provide your loving pet a healthy environment. Wonderful pet water fountain accessories. Perfect for pet_owner who want to provide clean drinking water for their furry friend and reduce the risk of urinary tract_infections. Specifications: Material: Sponges Diameter: Approx. 8cm/ 3.14in Note: 1: Please allow 1-2cms errors due to manual measurement, make sure that you do not mind before you order. 2: Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 4set Pet Water Fountain Filter