The 3M disc pad holder 9145 is a firm density holder with a 1/8 inch layer of foam, designed to hold a 4.5 inch Scotch-Brite™ Surface Conditioning Belt Disc on a right angle grinder or sander. The firm density of the pad supports an aggressive cut on flat sanding applications, and the thin layer of foam provides a slight cushion for professional results. The disc pad holder has a center hole with internal threads—choose the thread size that matches the external thread size of your right angle grinder. T-shaped hooks securely hold a surface conditioning disc and provide quick and easy disc attachment, removal, and re-attachment. It features the Hook-and-Loop System which enables the disc to be used and re-used for the extent of the abrasive life. Discs are sold separately. Max RPM is 13,000.