The pet fountain filter is composed of a cotton layer,activated carbon and an exchange resin.They can filter hair, heavy metals, and the of the water so that pets can drink clean and water. To keep drinking water and hygienic, it is recommended to replace the water fountain filter 2-3 weeks by thoroughly soaking the filter in water for 5-10 minutes use and installing it flat side up into the filter box. Compatible with 70oz/2.2L square pet fountain. This pet filters is easy to install,remove and replace. Triple filtration system: The pet water fountain uses an advanced filtration system. Colour:white+blue Material:resin Package Contents: 4 x filter 4 x blue sponge 4 x square 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.