PERFECTLY COMPATIBLE: Compatible with our cat water fountain and most square pet fountains. KEEP YOUR PET HEALTHY:This pet fountain filters consists of ion exchange resin, activated carbon and cotton mesh.They can improve the taste of the water and keep the water fresh so that pets can drink clean and fresh water all day. PREMIUM 6 PACK: 6-pack of premium cat fountain filters, individually packaged and sealed to maintain high quality. Size is 12.3cm*12.3cm*1 cm / 4.8*4.8*0.4 in. FREQUENCY OF REPLACEMENT: Change a cat water fountain filter 1 to 2 weeks in summer and 2 to 4 weeks in winter.If multiple cats are using the fountain, more frequent replacement will be necessary. NOTE: Flush the fountain with water before use and soak the filters in water for 2 minutes, then rinse thoroughly under running water before using.