The depth micrometer masters - models DM are available in both inches and millimeters.
The inch range is .500" ‐ 5.500" in 1.00" steps +/‐ .0001"
The metric range is 12.5 to 137.5mm in 25.0mm steps +/- .0025mm
They are case hardened, stabilized, black oxided, ground and lapped.
Depth micrometer masters are used to calibrate depth micrometers. It is superior to Gage Blocks calibration because they eliminate the requirement to stack gage blocks. Using a depth micrometer master is faster and more efficient for inspecting the linear range of the tool.