Abstract: Coupling sleeve with a generally cylindrical shape designed for connection between a mineral-insulated coaxial cable and a matching device which is itself coaxial. The sleeve protects a first contact and directly provides a second contact between two ends respectively of the cable and of the matching device. The sleeve is preferably designed with an aperture to enable filling after final assembly. The filling is done with insulating materials. After filling, the aperture is plugged. Preferably, the sleeve is soldered respectively to the second contact of the cable and to the second contact of the matching device.