This flail is a wear component for the threshing drum. It is mounted on the drum rotor and, as the drum rotates, the flail impacts the crop material against the concave, separating the grain from the straw and chaff. Flails are sold and installed in pairs, with each pair matched as closely as possible in weight. The two flails in a pair must be mounted on opposite sides of the drum to maintain rotational balance. After all flails are installed, the threshing drum must be balanced. When reconditioning the drum, replacing the entire set of flails is recommended to prevent shaft runout. A worn or mismatched set of flails causes vibration that accelerates bearing wear and reduces threshing efficiency.