Oh right. With a precision caliper no less. Another video posted here the other day used the word thou (as in thousandth of an inch) which is a word I haven’t heard in a long time!
Its frustrating. I'm a Canadian born and raised engineer/scientist working at a US-based medical device startup and I'm constantly converting between thou and microns and mm. Often stuff will be "in spec" for both, ex. 0.002" = 50um (assuming some tolerances for the part. Hopefully, we don't destroy any satellites by mixing the units up.