These are the smoothest, fastest cutting files you can buy. Nothing compares to diamonds. The rotary tone hole file set comes with 6 machined discs/pilots ranging from 12mm to 50mm in diameter (suitable for Altos & Tenors). The discs can be used to check the flatness of a tone hole by placing a disc (bare metal side down) over a tonehole and using a leak light. To file down high spots of a tone hole, the file is placed on the tonehole and turned with a wrench while applying pressure. The image above shows an assembled tone hole file and smaller disc for locating in the tonehole. The ball end allen wrench driver prevents tilting of the file on the tonehole. The JS tone hole files are essential for precision Saxophone work. Directions are included.