Replacement Filters for PETLIBRO Dockstream Battery Operated Cat Water Fountain PLWF005 PLWF115 Vertical Filtration System - 1. Activated carbon eliminates foul odors 2. Ion exchange resin removes heavy metal ions and softens water quality 3. The non-woven fabric captures cats' hair and impurities 4. The built-in pump sponge further filters debris to prevent blockages and damage. Every drop of water is filtered through multi-layer filtration to remove all impurities and provide oxygen-enriched and better-tasting water. To ensure better user experience, the cat fountain filter and pre-filter sponges are individually packaged. Soak the filter for 5 minutes and rinse for 30 seconds before use. To maintain the filtering effect, recommended to replace the filters every 2-4 weeks. If you have multiple pets, it is recommended to clean the fountain and change the filter more often.