• Triple action filter that purifies your cat's drinking water in 3 ways: 1. The cotton fabric filters impurities. 2. The activated carbon removes odors and impurities. 3. The ion exchange resin softens tap water. • Filter size: 8.3 x 8.3 cm. • The package includes 12 cat fountain filters. • Compatible with 2.5 L fountains. • Soak the filter in water for 15 minutes before use and rinse it. • Change the filter every 2-4 weeks depending on the frequency of use.