3M™ Paper Sheet 346U is constructed of aluminum oxide and comes in a range of grades and sizes to accommodate many different projects. The paper backing is durable for coarse sanding, yet flexible enough to be used on curved surfaces. Its cut-rate and durability make this an excellent choice for blending the joints of connecting pieces in wood- and metal-working. 3M™ Paper Sheet 346U contains aluminum oxide. Aluminum oxide is a very hard mineral that maintains sharp points on the grains much longer than natural abrasives such as emery or garnet. 3M™ Paper Sheet 346U also features open-coat construction, where abrasive grains are adhered to the sandpaper with space between them in order to minimize the buildup of dust on the surface of the paper when sanding softer materials. By minimizing dust build up and abrasive clogging open-coat construction elongates the useable life of the 3M™ Paper Sheet 346U.