The Lyman Case Length Headspace Gauge is perfect for reloaders looking to achieve the highest degree of safety and accuracy. Lyman recommends that all cases be inspected after resizing to ensure that the proper headspace dimension is maintained. Simply insert the case into the gauge to check that it does not exceed the maximum or fall below the minimum allowable headspace. If the case exceed the maximum allowable case length the case mouth will exceed the length of the gauge. Can also be used as a chamber gauge for loaded rounds.