A driver (3) for the transfer of torque and rotation from a rotation chuck (5) to a drill steel (2), whereby the cross-section of the driver (3) is limited outwards by curves, in particular by arcs, united to form a closed FIG. 6 that can be approximately described as a polygon, and limited inwards by splines (4). The FIG. 6 comprises four sides (7) and four corners (8). The splines (4) comprise a number of spline teeth (10), the number of which is divisible by four.