This rotary knife is a cutting element mounted in the straw chopper assembly. It rotates on its mounting pin to shear straw and residue against a stationary counter-knife, reducing material size for even spreading behind the combine. A worn or dull knife leaves ragged straw ends that increase the power draw on the chopper drive and produce uneven spread patterns. The original manufacturer's geometry matches the blade carrier's pivot bore and the counter-knife gap, so no shimming or adjustment is needed during replacement. On installation, verify the knife rotates freely on the pin and secure the retaining hardware to the specified torque.