Cat Water Fountain Filters: Composed of materials. Effectively to filter hair, heavy metals , keeps water fresh and improve the taste of the water Triple Filtration System: softens hard tap water so that pets can drink clean and fresh water from cat fountain, Helps pet to increase water consumption and reduce the risk of urinary tract infections. Wide Compatibility: Diameter of hollow circle is about 1.4 inch, Diameter of outer circle is about 5 inch, Compatible with most 84oz/2.5L Round cat fountain/pet fountains on market. [Keep Your Pet Healthy]Each filter is composed of materials. They can filter hair, heavy metals, and improve the taste of the water so that pets can drink clean and fresh water all day, which helps to increase water consumption and reduce the risk of urinary tract infections. Also, adding a pre-filter sponge around the pump to better filter impurities and extend pump life. Attention: To prevent the activated carbon dust from shedding into water, please soak for cat water fountain filters in water for 10 minutes then rinse thoroughly under running water before using. 1 to 2 weeks in summer and 2 to 4 weeks in winter. If multiple cats are using the fountain, more frequent replacement be necessary size: 10 x 10cm Material: Non-woven fabric + plastic colour: white+black Package Contents: 20 x filter elements 20 x sponge Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.