The Roomba 890 and 891 may be two different robots from iRobot, but they have exactly the same features; same tangle-free brushes, AeroForce 3-Stage Cleaning System, iAdapt Navigation, smart sensors, smart features and same performance. The differences are seen in the appearance of these two robots and included accessories. The 890 comes with a Dual Mode Virtual Wall and an extra filter while these items are not included in the 891 package, but you can buy them as extras for the 891.