Wide Compatibility: Our fountain filter fits most 1.6-2.5 liter cat fountains! Dimensions: outer diameter 127 mm, inner diameter 38 mm, thickness 10 mm. Effective filtration: The filter includes activated carbon and ion exchange resin, which can help remove chlorine, odors and contaminants, effectively filtering out dirt, encouraging your dogs and cats to drink more, and promoting 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 to ensure the best filtration. Then the installation is complete. 2-3 Week Change: We suggest changing every 2-3 weeks to ensure the best protective filtration for our animals.