The disclosure concerns a compression unit, in the form of wedge, of a transition for cables, pipes or wires. The wedge is to be placed inside a frame together with a number of compressible modules, which modules are to receive cables etc. The wedge comprises a number of wedge elements. The wedge is moved between non activated and activated positions by means of a screw, received in a through opening of a first wedge element, and a sleeve, received in an opening of a second wedge element. The wedge further comprises at least one clip, of an electrically conductive material, placed inside the wedge. The at least one clip is placed to connect the screw with the frame to connect the screw to earth.