Dust extraction back up pad constructed on foam material. Designed for use with Clean Sanding Hookit discs.. Includes 5 adaptors: 1/4-20 Ext x 5/16-24 Ext, 1/4-20 INT x 5/16-24 Ext, 1/4-28 Ext x 5/16-24 Ext, 5/16-24 Ext x 5/16-24 Ext, 5/16-24 Ext x 6mm-1.0 Ext