The 3M flap wheel, type 83 or type 84, is a general purpose flap wheel that delivers a consistent finish and uniform cut. Made of aluminum oxide on a firm, X-weight cloth backing, this product can be used in a variety of grinding and polishing applications. - Aluminum oxide 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, whereas traditional natural abrasives dull more quickly.