Idler pulley units are tensioning systems for belt drives and idler units: they increase the wrap angle in belt drives and can therefore support higher power levels or allow smaller units to be used they allow shorter centre distances they reduce the wear on the belt drive. The ready-to-fit units comprise deep drawn, profiled sheet steel pulley halves riveted together and deep groove ball bearings. Pulleys of larger diameters are additionally welded together. A lead chamfer on the pulley profile prevents damage to the belt. Due to the sheet steel construction, the additional rotating masses and the unbalance masses generated are low. Type A is suitable for vee belts, type B for flat, vee and round belts, type D for round belts, steel cables and hemp ropes.