The 3M disc pad holder 905 has a 5/16-24 threaded spindle and 1/4 inch foam and is compatible with 5 inch Scotch-Brite™ Surface Conditioning Belt Discs (sold separately) for use on a random orbital sander. A 1/4 inch layer of foam on the medium-density holder cushions the disc for professional results on flat sanding applications. T-shaped hooks securely hold a surface conditioning disc for quick and easy disc attachment, removal, and re-attachment. This feature enables the disc to be used and re-used for the extent of the abrasive life. Discs are sold separately. Max OPM is 12,000, and Max RPM is 10,000.