Amazon.com - Coodss Dual Model Virtual Wall Barrier Compatible with iRobot Roomba 500/600/700/800/900/e/i/s Series Robot Vacuum. Compare to Part 4636429 (Pack 2)
iRobot ROOMBA VIRTUAL WALL UNIT EXTENDED LIFE WALL BARRIER SENSOR!! | eBay
How To Install Batteries in a Virtual Wall | Roomba® 800 series | iRobot® - YouTube