Product Description 3M Disc Pad Hub has an internal threaded metal insert that threads onto the shaft of a sander and grinder to hold a disc pad face plate and fiber disc in place. From the Manufacturer The 3M™ Disc Pad Hub has an internal threaded metal insert that threads onto the shaft of a sander and grinder to hold a disc pad face plate and fiber disc in place. Hubs with a 4-1/2 inch diameter fit onto a larger rotary sander or right angle grinder and can hold a 7 inch, 8 inch, or 9 inch disc pad face plate. Those with a 2-1/2 inch diameter are suitable for 4 inch face plates as well as larger face plates where more flexibility is needed. The disc pad hub holds the face plate firmly in position to support a fiber disc with a 7/8 inch center hole, which is secured to the hub with a compatible retainer nut. The disc pad hub enables operators to select face plates with four different densities—Soft, Medium, Hard and Extra-Hard—offering the convenience of using a single power tool for multiple grinding applications. Face plates are sold separately.For more than a century, 3M has applied innovation and technology to improving our customers’ lives and supporting their business goals. Today the company, from its headquarters in St. Paul, Minnesota, serves industrial and commercial customers and consumers in nearly 200 countries. Abrasive Systems products, including a complete line of coated abrasives, microfinishing and microreplicated abrasives, and hardware accessories, provide the finishing touch for almost any surface conditioning application. The 3M brand, across thousands of products, represents consistency, superior quality, and value.