Our fountain filters fit most 1.6-2.5 liter cat fountains! Size: outer diameter 12.6cm, inner diameter 3.5cm, thickness 1cm. Effective filtration: The filter contains activated carbon and ion exchange resin to help remove chlorine, odors and contaminants, effectively filter dirt, encourage your dog and cat to drink more water and promote pet health and hygiene. EASY TO INSTALL: Rinse the fountain filter 3 to 5 minutes before use. Keep the filter completely wet to remove carbon dust and keep the flat side up for optimal filtration. Then the installation is completed. 2-3 Week Change: We recommend changing every 2-3 weeks to ensure the best protective filtration for our pets. TIP: Make sure the filter is the correct size for your fountain before purchasing and clean the filter thoroughly with water before use. Dimensions of the fountain product (LxWxH) 12.6 x 12.6 x 1 cm; 250g