[Compatibility] PET STANDARD Premium Water Filter ONLY Compatible with NPET WF020 Pet fountains. [Rectangular-Shaped Filter] Longest Side is about 4.7 inch. Width is about 1.10 inch. Thickness is about 0.80 inch. [Premium Quality Filters] Triple Filtration System: Composed of a Sponge Layer, activated carbon Layer and an ion exchange resin Layer. 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 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. [Premium 12 Pack Pet Fountain Filters] 12-pack of premium pet fountain replacement filters, individually packaged and sealed to maintain high quality. Enough supply for 4 to 18 months of use. PET STANDARD Premium Water Filter ONLY Compatible with NPET WF020 Pet fountains. Longest Side is about 4.7 inch. Width is about 1.10 inch. Thickness is about 0.80 inch. Triple Filtration System: Composed of a Sponge Layer, activated carbon Layer and an ion exchange resin Layer. 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. 12-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!