Professional Nail Files, Emery Board Nail File for Natural Nails 100/180/240 Grit Nail Files for Acrylic Nails 12pcs Fine Grit Nail File Manicure Tools Coarse Washable Fingernail Files Functions of Different nail files: 100 grit size - Coarse and rough. ideal for filling poly nail extension gel, acrylic nails and other hard tough nails. 180 grit size - Medium sharp and medium rough. ideal for filling artificial nails and nails edge. 240 grit size - Fine. ideal for final touches on poly nail extension gel and more usually for natural nails. Warmly Tips for choosing nail file: The higher grit it has, the finer the surface it gets and will be more suitable for soft nails. As there are differences for each nail, we only provide you a common advice, please choose the right grit according to ur needs.