This is a very versatile but easy to use gauge with a spring loaded foot. Check the depth of any hole or slot (up to 4 deep), check the runout of a table saw arbor or the flatness of a table saw blade. You can get your results any one of three ways that you prefer best: Inch, Metric or Fractional. The possible measuring range is 0 to 4" with an accuracy of 0.001", plus or minus 0.0005". Please note that the plunger does not travel 4". In common with many other dial and digital depth gauges the travel of the plunger is augmented by using precision plunger extensions.