Replacement 5-Pack iRobot Roomba 4210 Side Brush - For the iRobot Roomba 400 Series Brushes iRobot Roomba 4210 Side Brush Replacement Kit Includes 5 Side Brush It's best to replace your filters and brushes every 1 to 2 months The Brush allows your Roomba to reach deeper into the carpet for a more thorough cleaning