The brush roll has three settings (indicated by notches or numbers) on each side. You can adjust the height of the brush roll as it wears. The greater the number of notches, the farther the bristles are extended. To change the settings, follow instructions as replacing a belt, but when installing the brush roll, adjust the settings as desired. Always make sure they are on the same setting for both sides of the brush roll. When the bristles are at the greatest extension, you should consider replacing your brush roll to ensure maximum performance.