A coaxial gear set, in particular a hollow shaft gear set for industrial drive technology, having high power density, comprising a drive element (7), an element (3), and an output element, with a gear ratio and a transmission of a drive torque occurring between the drive element (7) and the output element via a plurality of radially movable tooth segments (5), an outer tooth flank contour (11.1, 11.2) of the tooth contour (6) of the tooth segments (5) and/or a flank contour (12.1, 12.2) of a gearing (13) of an inner gearing (15) of an internal wheel (1), relative to a gear axis (M), a tooth contour that allows surface contact in the engagement area comprising a logarithmic spiral.