Abstract: A transition piece for establishing a transition between a coaxial cable having an inner conductor and an outer conductor and a plug-in connector component having a plurality of terminals disposed adjacent one another, composed of a coupling member in the form of a coplanar stripline presenting a conductive strip and a conductive surface surrounding, and electrically insulated from, the conductive strip, the coupling member being connected to the coaxial cable and the connector component in such a manner that the inner conductor of the cable is connected to a point at one end of the conductive strip, the outer conductor of the cable is connected to the conductive surface, a first terminal of the connector component is connected to a point at the end of the conductive strip opposite its one end, and at least one terminal adjacent the first terminal is connected to the conductive surface.