1.[Compatibility] ONLY Compatible with a certain brand fountain, will NOT fit other brands. (Check shape and product dimensions). Compatible with certain design fountains and other specific models. NOT COMPATIBLE with the smaller fountain model. 2.[Round Pet Filter] Diameter of about 5.75 inches. Diameter of hollow circle is about 1.5 inches. Thickness is about 0.6 inches. 3.[Premium Quality Filters] Triple Filtration System: Composed of a cotton layer, activated carbon, and an ion exchange resin. Effectively filters hair and heavy metals, keeps water fresh, and enhances the taste of the water. 4.[Frequency Of Replacement] To prevent activated carbon dust from shedding into water, please soak the pet fountain filter in water for 10 minutes, then rinse thoroughly under running water before use. Replace every 1 to 2 weeks in summer and every 2 to 4 weeks in winter. If multiple pets are using the fountain, more frequent replacements will be necessary. 5.[Premium 6 Pack Pet Fountain Filters] 6-pack of premium pet fountain replacement filters, individually packaged and sealed to maintain high quality. Enough supply for 1.5 to 6 months of use.