Only compatible with WF020 Pet fountains. Longest Side is about 4.7 inch. Width is about 1.10 inch. Thickness is about 0.80 inch. Effectively to filter hair, heavy metals, keeps water fresh and improve the taste of the water. To prevent the activated carbon dust from shedding into water, please soak the cat fountain filter in water for 10 minutes then rinse thoroughly under running water before using. 1 to 4 weeks in summer and 2 to 6 weeks in winter. If multiple cats are using the fountain, more frequent replacement will be necessary. 6-pack of premium pet fountain replacement filters, individually packaged and sealed to maintain high quality. Enough supply for 4 to 18 months of use. Please feel free to contact us if you have any questions about our products, we'd like to help you!