Wide Compatibility: Our fountain filters fit most 1.6-2.5 liter cat fountains. Cut : 125*125mm, inner diameter 35mm. More efficient: the filter is equipped with activated carbon to help remove chlorine, odors and contaminants, effectively filtering dirt to provide water cool to cats. By using this filter, you can encourage your dogs and cats to drink more water and promote pet health and hygiene. Precautions for use: Please rinse the filter with water and make sure the filter is thoroughly wetted before installation. Keep the flat side up for installation. 2-3 Week Change: We recommend changing the filter every 2-3 weeks to ensure the best protective filtration for our pets . Scope of delivery: 12 fountain filters, square, white