High GAMMA disc-shaped tuning probes for high frequency electro-mechanical slide screw impedance tuners use a notch slug concept, whereby the head of the tuning probes is split in two distinct lobes in a static pre-matching configuration. The disc-probes rotate around an axis perpendicular to the axis of the slotted airline of the tuner and do not require a cumbersome vertical axis. The rotation moves the tuning lobes gradually into the slot of the airline and controls the amplitude of the reflection factor through increasing coupling. The disc-probes comprise two diametrical opposite tuning lob assemblies designed to create high reflection (GAMMA) at two distinct frequency bands, one for high end frequencies and one for low end frequencies.