Easy Maintenance: For best results, replace every 2 4 weeks ( more frequently with multiple pets) and always rinse with clean water before initial use to remove any loose charcoal bits Designed for Apuk APFSS 3201: This 16 pack pet fountain filter set works with the Apuk APFSS 3201 stainless steel water dispenser ( 3.2L capacity), providing proper sizing and smooth function for your pet ' s drinking needs Efficient Cleaning approach: Includes initial sponge layer for larger particles, tightly woven fabric cloth, natural charcoal for collecting debris, and chosen resin to improve water by lowering mineral levels Promotes Pet Health: The progressive cleaning process uses fabric, purifying charcoal, and selected resin to collect hair, unwanted minerals, and impurities while improving water taste, encouraging pets to drink more and reducing urinary issues Complete Replacement Package: Contains 16 cleaning units and 16 foam pieces ( each measuring 3.7x1.5 inches) made from PP fabric and sponge materials, providing long term use for keeping drinking water clean