Mitutoyo's Bi-Directional touch-signal probe is an optional accessory to be used with Mitutoyo's 192-series of Digimatic Height Gages. The Bi-Directional Touch Signal probe, when used with Mitutoyo's Digimatic Height Gage can quickly and accurately measure steps, inside width, and outside width. For use with the following Mitutoyo Height Gages... 192-670-10 (0-12" / 300mm) 192-671-10 (0-18" / 450mm) 192-672-10 (0-24" / 600mm) 192-673-10 (0-40" / 1000mm) 192-663-10 (0-300mm) 192-664-10 (0-600mm) 192-665-10 (0-1000mm)