Review on Proform 66902 High Valve Spring Height Micrometer - Ideal for V8 Engines by Christopher Jackson

I have just received this micrometer and have not used it yet. However, it appears easy to read and accurate when checked with calipers. However, I would be grateful if I knew how deep the interior step is. It just so happens that small Chevy mounts don't sit on top of the microphone; Instead, they sit on the inner step. With a step detent, the user must subtract the step depth from the specified height to get the true height of the spring. So it would be very helpful if Proform published this depth measurement. I assume depth can be measured with a dial gauge, but that's different equipment and another potential source of measurement error. Retainers of this size are very common, so I'm sure I'm not the only one with this problem.