The skin is made of silicon carbide with an extremely high abrasive ability. It is not as aggressive in the beginning, but it provides a high quality surface finish. Number of skins denotes the size of the abrasive grain - the lower the number - the larger the grain. The final choice depends on the number skins of work.
The approximate size of the abrasive grains - 35 microns.
1 sheet size - 230h280 mm.