A housing part for a measurement device, such as a radar level transmitter, with a fused glass or ceramic window and comprising: a single body (20) made of metal; the single body (20) has an outer circumferential side wall (2; 21) with an upper end (23) and a lower end (24) and an inner disc-shaped base wall (22) located at one of or between the upper and lower ends (23, 24), the side wall (21) and the base wall (22) defining one or two partially enclosed areas (25, 26); the base wall (22) comprises a flat circular center portion (27) surrounded by an annular zone (28) of reduced wall thickness on both upper and lower surfaces (31, 32) of the base wall (22); and the center portion (27) comprises a central hole (29) into which the glass or ceramic window (19; 30) is fused. The circular center portion (27) of the base wall projects above and below the surrounding annular zone (28) of reduced wall thickness, which allows for easier and more precisely machining. Microwave guides (33, 40) and, if necessary, dielectric matching elements (47, 48) are provided on both sides of the microwave-permeable window (30) to propagate microwaves between the desired points such as a radar antenna and the radar electronics. The waveguides can be press-fitted to the circular center portion for alignment and held by thrust collars (36, 43) having threads (37, 44). The dielectric matching elements may be accurately located and held in place by the respective waveguides on assembly. In this arrangement, the matching elements not only adjust the impedance of the microwave window to the impedances of the microwave guides but also put additional compression stress on the surfaces of the fused window, which are preferably ground flat to be flush with those of the center portion.