From the Manufacturer

For use with the Roomba intelligent robotic floorvac, this Virtual Wall Unit blocks open doorways up to 13+ feet wide! Compatible with Roomba FloorVac (Item #02001), sold separately Emits a harmless, invisible infrared barrier up to 13+ feet wide that Roomba will not cross Can be placed in a doorway to confine the sweeper to one room, or be used to divide a large room in half. The Virtual Wall Unit keeps Roomba in the room you want cleaned. Use extra Virtual Wall Units to: Block multiple open doorways OR Clean one portion of an extra-large room Requires 2 “D” batteries (not included)

Additional Virtual Wall