Abstract: A drive element (10) is provided for coupling together rotatable shafts (12) and (14). The shafts (12) and (14) are able to rotate about their respective longitudinal axes (12A) and (14A). Additionally, the shafts (12) and (14) can pivot relative to each other about a pivot point P which is coincident with the geometric center of the drive element (10). Drive element (10) includes a groove (20) for receiving a tongue (16) of shaft (12); and, a tongue (22) which is seated in a groove (18) formed in shaft (14). Surface (26) of the groove (20) and surfaces (34) on opposite sides of the tongue (22) are shaped so that as the axes of rotation (12A) and (14A) of the shafts (12) and (14) are pivoted relative to each other through a predetermined range of angles the respective loci of closest contact between the shafts (12) and (14) and the pivot point P remains constant.