This lock secures the spring on the hydraulic cylinder assembly of a combine harvester. It prevents the spring from dislodging during operation, maintaining tension on the cylinder return mechanism. A failed or missing lock allows the spring to shift, which can cause the cylinder to lose its return stroke and lead to erratic header or reel movement. This component is manufactured to the original geometry so it seats correctly in the spring retainer without modification. On reinstallation, verify the lock is fully engaged and the spring is seated against its stop.