A modular system of motorized conveyor rollers comprises a conveyor roller tube, a first axle unit, a second axle unit, a first bearing unit on a first tube end and a second bearing unit on a second tube end about which the conveyor roller tube is mounted rotatably about the first and second axle units, respectively, and an electric motor for generating a torque between the conveyor roller tube and the second axle unit. The modular system comprises, as the electric motor, a motor of a first design, which may be coupled to the conveyor roller tube via a first interface and to the second axle unit via a second interface, and a motor of a second design different from the first design, which may be coupled to the conveyor roller tube via the first interface and to the second axle unit via the second interface.