well, either there are, or my rather spendy mitutoyo digital calipers are broken. i just used them a few minutes ago... seem to be in excellent working order.

i also noted that i'd measured several 21.1mm stems too...

and i could have brought out my Micrometers to REALLY get a close reading....
and i was trained in Machine Shop Tech (4.0 graduate) when i was a young teen.. so... Yep... 21.7mm it is.

the "21.1mm" stems trend towards 21mm or slightly under, IIRC. old school and low school... one of the "21.1s" is still wearing the chromed schwinn shifters...

i could have gone into the hundredths of mm, and recorded each one, but i simply don't care or need to.