Fingernail and toenail file for shortening, shaping and polishing the hardest nails, filing on the medium grit side and outlining the contour on the fine grit side.
A high grit number (280-220) means that it is composed of many grains but very small, so the filing is softer. And a low grit number (120-180) indicates that the grain is coarser, recommended for shortening or initial filing.