Flat hand file. Dims. 230 x 38mm thick 1.55mm. Useful to get into narrow places where the sanding block is unable to fit. Use to clean up slots, cut-outs, formers, and general sanding.They may not be perfectly flat, they don't need to be, use the Perma-Grit sanding blocks which are.FINE grit is approx. equivalent to UK 320 / US 120 sandpaper.