This screw secures the header assembly to the drive mechanism on a grain harvester. It passes through the cover and washer stack to clamp the targańca (straw-walker drive) components together. The set includes the matching nut, washers, and cover needed for a complete installation. A screw of this hardness class maintains the required clamp load under the vibration and shock loads typical of the header drive. On reinstallation, clean the threads and torque the screw to the specification for the assembly.