compatible cat Fountain - The replacement filters are ONLYAcompatible with PETLIBRO cat water fountain PLWF005PLWF115PLWF105 In the Box - Package includes 4 packs of replacement filters and 4 packs of replacement pre-filter sponge To ensure better user experience the cat fountain filter and pre-filter sponges are individually packaged All For Your PetAs Health - Every drop of water is filtered through multi-layer filtration to remove all impurities and provide oxygen-enriched and better-tasting water 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 For Optimal Use - 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