In harvesting fine-grained product, reducing losses and increasing the purity of the harvested product has always been of great importance. The combine harvester, which is the main means of harvesting these types of products, has a cutting unit. The task of this unit is to cut the standing crop on the farm. One of the methods of reducing this unit's losses in fine-grained products is the use of a suitable head of combine harvester for harvesting these types of products. Regarding the necessity of this research, i introduce some of fine grain products which have more head loss. Moreover, i collected some of designs in this book which are using for harvesting these products.