A header has a middle section disposed on a base frame, and at least two side sections disposed adjacent the middle section and comprising a flexible cutter bar and at least one conveyor device located downstream of the cutter bar, which, on the respective side sections, is in the form of an endless belt disposed adjacent the middle section in order to transport crop cut by the cutter bar parallel to the longitudinal axis of the header in the direction of the middle section, wherein the side sections comprise a large number of supporting arms which are pivotably mounted on the base frame, wherein the supporting arms of the particular side section carry the cutter bar, and at least one supporting element is provided which carries at least one belt, thereby enabling them to move independently of one another.