stub structure 13 can be embodied in such a way that it is advantageously closable in particular in automated fashion the closing can be done in particular by means of a screw plug or peg structure fig5 sketches a concept by which an u201c enlarged wall portion u201d 1 a is created on the hard shell 1 or body structure specifically by designing the cross section of the body structure 1 such that it has a strutlike or wavy form the wall initially injection molded onto the wall portion 1 a here can then be lifted from this wall portion 1 a and in the corresponding cross section has essentially the same developed area or length width as the length width of the supporting wall 1 a fig6 shows a cross sectional sketch in which the wall 5 injection molded onto the wall portion 1 a has different wall thicknesses adapting these wall thicknesses makes it possible to exert influence on the mechanical properties of the gel structure that is finally to be formed in cooperation with the wall 5 the mechanical properties of the sealing lip device 2 a resting on the area g of a user 39 s face can also be defined by special designing of the course of the wall thickness and of the profiling of the sealing lip device as shown in sketchlike form in fig7 a an embodiment of the invention for forming a gel receiving chamber ga can be realized especially advantageously by.