Superior Pads and Abrasives RSP39 6" Dia No Vacuum Holes PSA/Adhesive Back Sanding Pad Replaces Porter Cable 16000. The pad sands flat surfaces to their smoothest and features built-in mounting thread for quick and efficient installation. The 6-inch diameter easily accommodates 6-inch adhesive-backed sanding discs and protects the discs from damage. Note: For use with 6" discs. 5/16"-24 thread shaft diameter maximum 10,000 RPM.