The Speed-Lok quick-change system allows for easy disc mounting and removal to maximize productivity * Aluminum oxide is durable and the most common abrasive grain * Heavy cotton backing is heat-resistant, durable, and flexible, for use on contours or flat surfaces * TR discs have threaded central hubs that require two-and-a-half turns and mount to Norton TR or 3M Roloc TR backing pads * This disc is used with a molded rubber backing pad (sold separately)