So millimeters, then? :) "M" is used quite frequently for million along with "K" for thousand. "MM" as million is used in conjunction with "M" for thousand, bu

So millimeters, then? :) "M" is used quite frequently for million along with "K" for thousand. "MM" as million is used in conjunction with "M" for thousand, but that's a different notation set. "M" & "K" usage is generally much more popular than "MM" and "M", at least in any areas I've been.