3M™ Flexible Diamond Hand File 6210J includes micron graded diamond mineral anchored to a rigid plastic file in a metal bond matrix with an open dot pattern. It's ideal for deburring and finishing non-ferrous metals, as well as stone, glass and ceramic materials. - 3M Flexible diamond hand file 6210J was created to help operators gain instant access to the workpiece by incorporating our diamond material into a hand-held design. For those parts that may have hard-to-reach areas or edges that may be hard to access, a hand tool sometimes proves itself to be the best solution.