A gear motor series has two pinions with different numbers of teeth (z1a, z1b), and several toothed wheels with different numbers of teeth (z2a, z3a, z4a). The pinions and the toothed wheels are designed such that each pinion, in several predetermined axial distances (a), can be paired with one of the toothed wheels in order to form a first gear stage. One individual toothed wheel is provided for each predetermined axial distance (a), which is embodied such that it can be optionally paired with the one pinion or with the other pinion to form a first gear stage.