Sanding belts. What size fits in your belt sander.

Belt sanders can have a very aggressive action on wood and are normally used only for the beginning stages of the sanding process, or used to rapidly remove material. Sometimes they are also used for removing paints or finishes from wood. Fitted with fine grit sand paper, a belt sander can be used to achieve a completely smooth surface. Stationary belt sanders are used for removing non-ferrous metals, such as aluminum. Non-ferrous metals tend to clog grinding wheels, quickly making them useless for grinding soft metals. Because the small grooves in the sandpaper are opened up as they go around the arc of the drive wheel, belt sanders are less prone to clogging (wikipedia).