The 3M Disc Back-up Pad Mounting Kit is designed to mount the one-piece Disc Pad Face Plate to most standard angle grinders. Each kit includes a Retainer Nut and two sizes of Wheel Spacers. Some tools may need additional spacers to ensure a proper fit.The Full System Advantage Eliminate the guesswork of fitting washers and tools with the 3M Disc Back-up Pad Mounting Kit. This kit ensures a proper fit between your angle grinder and the 3M Disc Back-up Pad. When you combine this upgraded disc back-up pad with 3M Cubitron II Fibre Discs or select Scotch-Brite Abrasives, and a 3M Angle Grinder, you’re setting yourself up for a new level of productivity. When used together, the effectiveness of each component is enhanced to provide optimal abrasive performance — including abrasive life, cut-rate and consistency.