Abstract: A heat-expandable tube-like component includes a tubular wall having a length dimension and defining an inner space; and a septum attached to the tubular wall and dividing the inner space into separate, longitudinally extending passages. The septum has a weakened portion which includes first and second groove-like recesses in opposite faces of the septum. The first recess extends substantially parallel to the length dimension (axial dimension) of the tubular wall. The second groove-like recess extends slightly offset from and parallel to the first groove-like recess. Further, portions of the septum flanked by the first and second recesses are sufficiently weak to break under the effect of forces derived from heat-caused expansion of the component. Also, the recesses are so arranged with respect to one another that upon breakage of the septum portions flanked by the recesses the septum halves obtained by the breakage are adapted to glide past one another.