The stock Black CHM was manufactured by iRobot with two shielded ball bearings inside to help prevent the entry of dust and debris into the brush gear assembly.  After some use, the two bearings themselves become full of dust and debris that prevents the brushes from turning.  This causes the Roomba to complain with the "Please Inspect and Clean Roombas Brushes" error.  I offer a solution to that issue by providing you two Sealed ball bearings to replace the inferior shielded bearings that came with your Black CHM.  This solution is available for just $30 plus $2 USPS shipping.  Just paypal $32 to e_vickery@bellsouth.net