To determine the grain size, coffee is sifted through a stack of special screen screens. Each screen has its own size holes: the top screen in the stack is the largest, the bottom one is the smallest. Sifting coffee through such a simple device, the grains are sorted by size. Classification starts from screen 20 and ends with screen 8. There are also intermediate screens – for example, 15/16 or 17/18 screens. The larger the grain, the more nutrients the grains received during maturation.