Abstract: Planetary reduction gear mounted in the tube of a tubular motor. The reduction gear has at least one input stage and one output stage and a satellite holder secured to the output shaft of the reduction gear. The ring gear of the reduction gear has two parts rotationally immobilized in the tube and one part meshes with the satellites of the input stage and the other part meshes with the satellites of the output stage. The two ring gear parts are connected to one another by a connection component interlocked axially in each of the two ring gear parts and fixed to the tube. This allows the ring gear to be immobilized more completely; the diameter of the output shaft may be greater and the reduction gear may be designed ion a modular form.