In a reproducing machine the photoconductive member, in the form of an endless belt, and the developing station are carried in a container or cartridge removably mounted on the machine. The photoconductive belt surrounds a support structure integral with the cartridge. The support structure includes a resilient portion engaging the photoconductive belt to keep it under tension around the structure. A magnetic belt of tubular form, fixed within the cartridge, is surrounded by a sleeve of non-magnetic material. The magnetic belt is so magnetized as to form a regular distribution of pairs of magnetic poles of opposite polarity. The toner adheres by magnetic action on the external surface of the sleeve to form a magnetic brush of the developing station.