SEBO’s new automatic X4 boost. Features two truly automatic height settings that enable the user to choose between two levels of brush agitation! The default setting is perfect for most flooring types. But by activating the Boost Button, greater resistance against the spinning brush roller is allowed before height adjustments are made, which causes more aggressive brush action. For users who want truly automatic height adjustment, but also want to choose their level of brush aggressiveness, the X4 boost is the solution!