3 inch Flex Pro Professional Backing Plate with Drill & DA Adapters. Molded urethane backing plate. Nothing holds pads better than our Hook & Loop flexible backing plates. The Flex Pro 3" inch backing plate comes with both a drill attachments (¼" shank fits most drills) that enables you to use it with most any drill of your choice and Porter Cable or DA adapter (standard 5/16"). Flexible Backing Plates minimize heat transfer, while it flexes just enough to contour to your autos bends curves.