Quad pack of 4 - iRobot Scheduling Virtual walls. Not in retail package. A Virtual Wall emits an adjustable infrared beam (up to 13 feet) that prevents Roomba from entering off-limit areas in your home. Scheduling capability allows you to preset cleaning times so your home robot cleans routinely, when it's most convenient for you. Each wall requires 2 D batteries (not included). Requires iRobot Scheduler Remote to activate scheduling capability (not included).