This component is a flow restrictor for the seed-metering system of a grain drill. It regulates the rate of seed or fertilizer material passing through the pneumatic distribution lines, ensuring consistent delivery to each outlet. The restrictor inserts into the distribution head or manifold, where it creates a controlled pressure drop to balance flow across multiple runs. A worn or missing restrictor causes uneven distribution, leading to over- or under-seeding in individual rows. The manufacturer's original design matches the internal bore profile of the manifold for correct flow calibration.