This belt tensioner maintains the correct drive-belt tension in the threshing mechanism drive. It is installed on the tensioning arm that presses against the belt span between the drive pulley and the driven pulley. A worn tensioner allows belt slip, which reduces threshing drum speed and causes uneven crop flow. The assembly includes the pulley, bearing, and mounting hardware for a direct replacement. On installation, ensure the mounting bolt is torqued to specification and that the belt aligns with the pulley groove.