Compatibility: These replacement filters are exclusive to the NPET 050TP pet water fountain. Includes 4 filters in a set. Easy to use: simply rinse the filter under running water for 10 minutes before using. Powerful filtration function: high-density and high-content activated carbon filters, combined with high-density white cotton, ensure higher water quality and higher oxygen content to keep your pets healthy. Note: Clean the filter once a week and replace it every 4-8 weeks. If more than one pet shares the fountain, clean the filter more frequently.