This rotary chopper knife is the cutting element mounted on the chopper drum of a forage harvester. It shears crop material against a stationary shear bar as the drum rotates, reducing the harvested plant matter to the desired chop length. The knife is a flat, hardened steel blade with a mounting hole for bolting to the drum. Wear on the cutting edge reduces chopping efficiency and increases power draw; a dull knife produces ragged cuts and requires more energy from the driveline. This original component matches the factory-specified blade profile and mounting geometry, so it seats correctly against the drum without shimming. When replacing, inspect the shear bar for wear and replace it if the gap between the bar and the new knife exceeds the specified clearance.