3M Hookit 236U Hook & Loop Disc 55582 - Aluminum Oxide - 5 in - P400. 3M Hookit coated 236U hook & loop disc uses aluminum oxide as the abrasive material and has a diameter of 5 in. 3M incorporates this aluminum oxide material into the hook & loop disc forming a grit of P500. This abrasive is on a paper backing, C weight. All abrasive products that rotate or spin, such as the ones in this category, have a maximum speed at which you can run them. This 3M hook & loop disc can be run at a maximum speed of 12000 RPMs.