I was concerned about the cheapness and the dial on the side didn't make much sense. But you use 'Test' mode to zero the gauge, and then 'Using' mode unlocks the full range of motion. This protects the device if you miss while moving down so you don't crush the indicator and damage your bit, a nice feature. It's a really great tool and it fits my VMC's CI, so I guess it's good enough for what I'm working on.