An automatic microwave load pull slide screw tuner uses two RF probes, either independently movable or linked together, in order to generate high VSWR; precise alignment of two RF probes inside the same slabline is critical, since they must glide seamlessly inside the slabline slot, very closely to the center conductor over large horizontal displacements; a self-alignment mounting joint for the probes is described, which allows one or both of them to be mounted on the tuner's vertical axis held by a flexible steel blade, which allows sidewise movement and tilting and self-alignment of the probe, but also ensures unyielding movement in vertical and horizontal directions, as required for exact re-positioning of the probe during measurement. In case of double probes mounted on the same tuner axis the steel blade provides for a number of probe spacings, which allow the frequency range of the tuner to be switched for various applications.