The DeWalt DW4945 is a 4-1/2 Steel Reinforced Rubber Backing Pad with 5/8-11 Locking Nut. The quick change rubber backing pad comes with all things needed to replace worn out 4-1/2 backing pad. The backing pad is a crucial component for attaching sanding discs, foam bonnets and polishing bonnets. The rubber backing pad is designed to work at a maximum of 12000 RPM.