The desired length of the strip can be torn from the roll for a specific application. Most grades have a light, J-weight cloth backing that provides the flexibility needed to conform to circular edges, angles, or other contours. Rolls in grades P50 or P60 have a slightly stiffer X-weight backing suitable for more coarse sanding applications. Cloth remains durable even when bent or rolled, without tearing or shelling, but strips can be torn by hand when a smaller piece is needed, without compromising the sanding surface.
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. Aluminum oxide is suitable for a wide variety of materials in both woodworking and metalworking, including ferrous alloys. Aluminum oxide abrasive can be used on ferrous and non-ferrous metals, wood, and plastic.

3M 05009, Utility Cloth Roll 211K, 100 J-weight, 1 in x 50 yd, Full-flex, 7100016843
3M 20922, PSA Cloth Disc 348D, 60 X-weight, 1-1/2 in x NH, Die 150S, 7010326528.
Dynabrade 77772 5" Dia. x 7/8" Center Hole, 40 Grit, Type 27, Ceramic DynaCut Flap Disc, 10/pack 
