I bought these to clean the extrusion nozzle on my 3D printer. But it's one of those multipurpose tools that you might not have guessed needed for a multitude of things. I had a brass fitting that needed fresh tape on the threads, but I was having a hard time getting the old tape out of the slots. Then I remembered I had these brushes and one of them quickly solved the problem I was struggling with. Since the bristles are brass, I didn't have to worry about the threads breaking. Now the hardware is like new again.