The Bergeon 6240 scratch brush is made to get into small areas for cleaning and finishing. This scratch brush is designed like a pen for comfort gripping and use, and features a pre-shaped, spring loaded thumb mechanism that controls how much of the scratch brush bristles are exposed. You can get in close to clean hard to reach places, remove rust from small parts, & apply matte finishes. It is great for working in tight places and for electronic applications. Diameter: 2 mm