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 fibre disc in place. 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 fibre 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 fibre disc with a 7/8 inch centre 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.