Abstract: When packing articles, particularly sheet stacks, such as computer lists, for transportation and dispatch purposes in a film, thick stacks should be tightly enveloped with a shrink film envelope, so as to increase their transportation stability, whereas the envelope of thin stacks is to remain unshrunk, so as not to deform the stack. It is proposed that both types of articles be passed in the packing line through the shrinkage tunnel, but in the case of articles not to be shrunk by increasing the passage speed and/or decreasing the circulating air speed, the heat transfer conditions are reduced in such a way that no shrinkage occurs. It is also proposed to so control the welding dies or jaws of a longitudinal welding station as a function of the thickness of the articles that thinner packs are more tightly enveloped than thicker packs.