The present invention concerns a compression wedge of a lead-through system. The compression wedge comprises a number of wedge elements (1, 2, 3, 4). At least one of the wedge elements (1, 2, 3, 4) has a core (9, 10, 11, 12) of a harder material than an outer part surrounding the core (9, 10, 11, 12). The part surrounding the core (9, 10, 11, 12) is made of an elastic material. The wedge is moved between a non-compression state and a compression state by means of one single screw (6) co-operating with a socket (7).