Wide Compatibility: Our fountain filter fits most 2-2.5L cat fountains! Dimensions: outer diameter 125 mm, inner diameter 37 mm, thickness 10 mm Better filtration: non-woven. Dumps sundries, absorbs heavy metals and eliminates odors. Protect your kitten from unwanted infections. Give them healthier, tastier juices! RINSE AND REMOVE: Rinse the fountain filter for 10 minutes before use to remove charcoal dust. Please turn the flat surface up to ensure the best filtering effect! 2-4 Weeks Replacement: Although our fountain filter lasts a long time, to ensure the best protective filtration for our pets , we recommend changing it every 2-4 weeks. Individually packaged, each fountain filter element can be easily stored and stored properly for best results!