What is the lightest weight category for sandpaper?

The lightest weight category for sandpaper is designated as A weight. This classification indicates that the paper is lightweight and typically used for fine finishing tasks. The A weight sandpaper has a lighter backing, which makes it flexible and better suited for sanding on curved surfaces or delicate materials.

The other weight classifications, such as C, E, and X, correspond to heavier paper grades that have increased durability and are appropriate for more aggressive sanding tasks. Therefore, A weight is specifically tailored for finer applications where a lighter, more flexible approach is necessary, making it the lightest option among the listed categories.