GP12604 Hook and Loop Rotary Backing Pad with 5/8''-11 Thread, Sanding, Polishing Backer / Diameter 4.5 inch Diameter: 4.5 inch Thread size : 5/8''-11 Density: Medium Semi-Flexi 10mm Foam Interface: Hook and Loop fastener ( Velcro Type), Max RPM: 12,500 Ideal for high speed sanding, polishing flat surface