Abstract: A mount is provided from which a pair of laterally spaced and registered oppositely tapering parallel cones are journaled. A cage is guidingly supported from the mount for adjusted shifting along and between parallel planes containing the adjacent sides of the cones and a spherical power transmission member is universally rollingly supported from the cage and includes diametrically opposite surface portions tightly frictionally rollingly engaged with opposing surfaces of the cones and adjustment structure is provided for shifting the cage lengthwise of the cones.