Grit is a term used in defining the coarseness or texture of abrasives; grit is measured in numbers; a lower grit (fewer grit particles per square inch) is more coarse. Nail file grits range from 60-80 (extra coarse) to 900-1,200 (buffers). Lower-grit files are used for reducing the length of and shaping acrylic or gel nails. Higher-grit files may be used for finish work, nail prep, and for smoothing and shining artificial or natural nails.