A hearing aid includes a shaped body that is adapted to an individual auditory canal. A casting cavity is created from a central casting space element, an outer casting space element, and a canal element. The casting cavity is filled while inside the auditory canal. The central casting space element, which remains on the hearing aid, has an outer and an inner ring as well as a tubular and extendible membrane. The outer casting space element delimits the casting cavity on the outer face. After casting, the outer casting space element is replaced by an electronics module including a loudspeaker. The at least partly flexible canal element can hold the loudspeaker canal open, can be joined in a fixed or detachable manner to the outer casting space element, and can essentially close the opening of the inner ring and can limit the axial mobility of the inner ring.