The Brondell H2O+ Cypress Composite Plus filter (HF-31) utilizes 2-step filtration technology to actively reduce particulate materials such as sand, rust and fine particulates from the water supply. This first of three filters acts as a pre-filter protecting the following two additional filters. With its quick connect system, filter replacement is a snap. Recommended replacement every 6 months. Choose Brondell H2O+ for better water.