iRobot Roomba Model 4220 Vacuum Cleaning Robot effectively cleans both carpets and hard floors. Roomba cleans hard to reach areas like wall-edges and beneath furniture. It automatically avoids stairs and other drop-offs and Roomba even senses dirtier areas and cleans more thoroughly in those spots. At the end of a cleaning cycle or when its battery is running low, Roomba returns to its Home Base to recharge. Roomba comes with 2 virtual walls that keep Roomba cleaning where you want it and out of off-limit areas.