A Scratch Brush allows access to sand and clean hard to reach areas. Goes where sandpaper, files, and other tools cannot reach.
Great for cleansing electrical contacts and removing rust and corrosion from surfaces with lots of details and texture. Also used to sand around tiny chips in paint before touchup, prepping surfaces for glue, and cleaning soldering pads on PCBs.
Fiberglass, it is a skin irritant and you don't want to get it in your eyes. Avoid touching tip and be careful with the dust produced.