These small brushes have bristles that are .005" diameter which make them great for applications where you need something that small to fit. Cleaning the spaces between the fins in a 51 collector comes to mind. These brushes, with a little Simichrome polish, are also great for getting the black patina (Gunk) out of those little tiny characters making up the imprints on light colored pens, like Mandarin and red/orange, cream, coral, or light green. Try them on cleaning threads on light colored pens, also. These are soft, tiny bristles, great for cleaning corners, crevices, & tiny areas. they fit inside most barrels and caps, also. They don't scratch. I use these a lot for cleaning and removing polishing residue in my own work on pens. A: 3/8"DIA, 6.5"L, BLACK BRISTLES, METAL HANDLEB: "Miro's Brush" OUT OF STOCK because Miro bought them allC: 3/8" DIA, 6.25"L, Black Nylon, METAL HANDLED: 9/32" DIA, 5"L, WHITE BRISTELS, METAL HANDLE