Topic summary
Sanding
Extracted from the Wikipedia article Sandpaper.
Backing
Cloth backing typically comes in weights "J", "X" and "Y", from lightest to heaviest. Additional weight designators also exist, like "JF" or "XF" for variants with extra flexibility or "YY" for an even heavier option. Cloth is preferred for its high durability, and used in applications such as sanding belts.