There are a multitude of nail files on the market with different grain. This is expressed in grit and indicated by corresponding numbers on the nail file or its packaging. This unit indicates how many grains are in one square centimeter of the file.
The smaller the number, the fewer grains on the lime, but the larger they are. These files are coarse and sharp, they are used to remove a lot of material and have for example a value of about 100. The finer files have smaller but more grits in a square centimeter and are suitable for softer sanding and have for example a value of 180.
Often, a file has two different grains on its two faces (coarse and fine) – these are then indicated both in the form 100/180 for example. Buffing blocks are particularly fine and suitable for final polishing of the nail. They can have a very fine grain, around 3000.