[Compatible]: This cat water fountain filter is compatible with a variety of cat fountains, the specific compatible fountain style, please check the product image list, before buying please confirm whether it is compatible with your cat fountain to avoid purchasing errors. [Filter]: The cat fountain filter helps filter the water quality, while the pre-filter sponges blocks out any hair, dust or food debris. [Material]: The pet fountain filter is made of safe materials, which helps keep the water fresh and allows pets to drink fresh water. [Note]: Before use, soak and flush the cat water fountain filter with clean water,clean the filter every time you change the water of the cat fountain, and change the cat drinking fountain filter and sponge every 2-4 weeks.