The optigear Shaft Mounted Speed Reducer provides a very convenient method of reducing speed, since it is mounted directly on the driven shaft instead of requiring foundations of its own. It eliminates the use of one and sometimes two flexible couplings and external belt take-up arrangements. A torque-arm anchors the Reducer and provides quick easy adjustment of the V-Belts by means of its turnbuckle. The Optigear Speed Reducer is manufactured in eight gear case sizes, designated by the letters B to J. The eight sizes may have anyone of three nominal gear ratios 5: 1, 13:1 and 20: 1.