I bought this product (DerBlue Replacement Parts for iRobot Roomba 860, 880, 805, 860, 980, 960) and the first set of Tangle-free caster wheels worked but when I got them replaced with a second set and my Roomba kept telling me to clean the vacuum cleaners in just a few minutes. They are brand new and I have tried cleaning and putting them back 5 times now. Not worth saving. The DerBlue 3-ArmedSide brush also failed. I just went to online ordering to order genuine iRobot Roomba 800 and 900 series accessory kits. I prefer offers, but only if they work!