Primarily used by turners, these thickness calipers can be fitted into virtually any shape of vase or bowl. To use, open the caliper by just pulling the legs apart (having the spacing nut between the legs rather than outside them allows this), put in position and then set the spacing nut to the wall thickness. Open calipers, remove and measure tip gap. The spacing nut can be adjusted for any thickness from 0 to 343mm on the 420mm model and 0 to 140mm on the 230mm model. The respective throat depths (from nut to tip) are 292mm and 140mm. These are equally good for dimensional take-offs of almost any oddly shaped object. Steel with brass fittings. Made in France.