Abstract: Apparatus for shaping a tubular preform into a hollow body in which an axially directed wall of the preform primarily comprises oriented and/or crystallized plastic material. The tubular preform (10d) is fixed in a circumferential region (13d) in the vicinity of the mouth edge (14d) of the preform between mechanical forming devices (30,40), after which the devices, during continued clamping of the circumferential region, are displaced in the axial direction of the preform relative to a mandrel (50). Thus, the mandrel is displaced into the preform during simultaneous expansion thereof and the material is oriented and/or crystallized. In a preferred embodiment, there is compensation of the stretching forces, which arise in the material when inserting the mandrel, by applying a force to the bottom of the preform by a bottom support (75).