According to reviews many problems with these aftermarket parts are due to how they fit and that some orders do not fit all models even within the 600 series. These parts were a slightly larger than the original Roomba parts, the brush bristles are slightly longer, the filter is slightly denser. I attribute this to design or manufacturing tolerances by these second suppliers. But everything came together, Roomba worked and cleaned normally, so this is tremendous value compared to the price of Roomba.