The Automatic X4 Boost 90504AM is the world's most technically advanced and uniquely designed vacuum cleaner. The easy to use X4 Boost features a 12" brush roller that automatically adjusts to any carpet pile using a electronic controller that measures the resistance of the spinning brush roller against the floor to signal the vacuum to adjust the roller up or down. This will ensure optimal performance on both carpets and hard flooring. The 90504AM SEBO X4 Boost also alerts you when there is a clog, worn brush roller, or when the dust bag is full. The X4 Boost offers two modes of brush agitation. The default setting is ideal for most types of flooring. By activating the boost button, causing the brush roller to spin more aggressively.