Replacement filters for pet fountains: With double action water softener filter for ion exchange resin and activated carbon which can filter dirt effectively. The quantity of 12 packs meets the daily needs of your pet. 3-stage filtration: It helps to remove chlorine, filter hair residue and heavy metals, eliminate peculiar odors, soften and improve the quality of your pet. 'water. Provide healthy and hygienic water for your pet and take care of their health. Green Material: The pet fountain filter is made of high quality polyester pad, carbon high quality active and ion exchange resin. It has the function of cleansing and activating, which belongs to the green purification method. Safe and non-toxic. Perfect match: inner diameter 3.5cm, outer diameter 12.5cm. Compatible with many round water fountains. Please confirm the product size before purchase. Replacement frequency: Replace the filter every 4 weeks, and replace it more frequently with multiple pets using the fountain. To prevent dust activated carbon spills in the water, please rinse the filter thoroughly with water before using.