Replacement filters for pet water fountains, designed to keep your pet's drinking water clean and fresh. These circular filters feature activated carbon and multiple filtration layers to remove impurities, odors, and debris from the water. Key features: • Compatible with standard pet water fountains • Multi-layer filtration system • Contains activated carbon for odor removal • Circular design with center hole • Comes in a pack of multiple filters • Easy to replace These filters should be replaced every 2-4 weeks depending on usage and number of pets. The activated carbon helps remove bad tastes and odors while the filter material traps hair, dirt and other debris. Regular filter changes help maintain water quality and extend the life of your pet fountain pump. The filters appear to use coconut shell carbon for natural filtration.