Made to measure the depth of holes - wider and thinner than the original iGaging one to make it more versatile. Primary use for mine is measuring tyre tread depth... This will slip on to most brands of calipers, it is not a tight fit but will sit square. The base is 1mm thick, place on a flat surface, extend the depth gauge and zero there if you're using digital calipers. 2 models, see instructions.One model is the straight slip on version, print at 20% infill, 2x perimiters and it won't use much material at all. No supports needed. The second model will take a captive M3 nut and M3x25mm bolt. This will let you cinch the bolt down to hold it more firmly. Doesn't need supports, will use up more material as your slicer builds internal support structures.