Radial Bristle Disk Hub for use with 3" Bristle Radial Disks and Benchtop Polisher. Customize the thickness of your disk by stacking the exact number of plys you need. Depending on the application, you will want to stack between three and six disks. NOTE: Always place discs on the mandrel so that the bristles curve opposite (or away) from the direction of rotation -- bristles should not be bent backward during use. Be sure to closely follow the directions in the package so that the disks are stacked and mounted properly onto a handpiece or the bench lathe.