This disc is the metering plate for the fertilizer coulter on a Monosem precision drill. It rotates within the coulter housing, controlling the flow of granular fertilizer from the hopper to the furrow opener. The pattern of holes in the plate determines the application rate; a worn or damaged disc causes uneven distribution and streaking in the field. This original Monosem component is machined to the same thickness and hole geometry as the factory-installed plate, so it seats correctly in the housing without modification. On installation, ensure the retaining clip is fully engaged and that the disc rotates freely against the housing face.