3M Xtract™ Paper Disc 216U is constructed of aluminum oxide and is suitable for finishing applications on wood as well as primer, paint, sealers, topcoats, fiberglass, and plastics. The 3M™ Hookit™ (hook-and-loop) attachment system makes disc changes fast and easy, meaning the disc can be used again and again for the extent of the abrasive life. Part of the 3M Xtract™ Series, designed for optimal dust removal. For maximum dust extraction, use this disc with a 3M Xtract™ Back-up pad and a random orbital sander with vacuum (both sold separately). We chose aluminum oxide abrasive, which is a popular choice among industrial professionals because of its fast cut-rate and long life. This mineral makes a tough, durable abrasive that self-fractures to expose fresh cutting edges in use, whereas traditional abrasives such as garnet quickly wear down with use. Due to their fast cut-rate, hardness, and strength, they are widely used in sanding and finishing applications. Aluminum oxide is suitable for a wide variety of materials in both woodworking and metalworking, including ferrous alloys.