Jason Variable Speed belts are for use on variable speed pulley drives requiring exact speed control and maximum range of speed changes. Variable speed drives are employed where the operating speed of the driven pulley must vary over a wider range. Axial movement of the variable speed pulley flange changes the pitch diameter (radial position) of the belt and therefore belt speed, and so the rotational speed of the driven pulley. The sidewalls of the belt conform to the angular faces of the pulley flanges.</p>