This rubber tensioner applies constant radial force to a belt or hose within the header's threshing mechanism. It maintains the correct drive tension between the upstream pulley and the downstream driven component, preventing slip during variable load conditions. A tensioner that loses its spring rate or develops a flat spot on the contact surface allows belt flutter, which accelerates wear on the belt and the bearings of adjacent pulleys. This component is manufactured to the same internal and external diameters as the original assembly, so the mounting fit and the belt-wrap geometry are preserved without shimming. On installation, verify the tensioner arm moves freely through its full arc before the belt is seated.