Formed by a single block of reinforced rubber, whose peculiar geometric characteristics allow the required excursion, with the steel inserts arranged in such a way as to be present in any vertical section of the panel.
The PLK series models are characterized by the absence of a central bellows, so that the movements are supported by the "stretching" of the rubber part. It is vulcanised on three sheets, two of which are base sheets and the third is placed at a higher level, separated by an appropriate layer of rubber.