This set of four collet brushes are sized for the four most popular collet sizes: 1/4", 3/8", 1/2", 6mm, 8mm, 10mm and 12mm. With twisted steel handles, the bristles are made from brass wire to prevent damage to the collet. The brushes are used to remove corrosion, dust and resin deposits from the hard to reach insides of collets. Excessive build-up of dust and swarf will cause the router to cut in an elliptical fashion, resulting in poor quality cuts. Removing the resin and dust from the collets removes this problem and allows you to work considerably more precisely. ©