[Compatibility] PETSTANDARD Replacement Filter Compatible with WOPET® Water Fountain. These are PET STANDARD branded filters and are not created or sold by WOPET®. [Premium 10 Pack Pet Fountain Filters] Pack of 10 Filters and 4 Replacement Pre-Filter Sponges [Compatible Pet Filter] Filter Measurments: 2.5" x 1.5" x 1.25" [Premium Quality Filters] Triple Filtration System: Composed of a cotton layer, carbon prefilter and activated carbon. Effectively to filter hair, heavy metals, keeps water fresh and improve the taste of the water. [Frequency Of Replacement] To prevent the activated carbon dust from shedding into water, please soak the cat fountain filter in water for 2 minutes then rinse thoroughly under running water before using. Change every 2 to keep water running fresh and pure. Change the filter every 1 week will be healthier! [Friendly Customer Service] Please feel free to contact us if you have any questions about our products, we'd like to help you!