Measurement Notations

I am looking at the PCB footprint diagram of a DC-DC converter (and some other stuff like the measurements on servo splines, etc.) And there is a symbol that I am not sure about.

The symbol is: ø

For example:

Servo horn gear spline: 24 segment/ø0.576

An arrow pointing to a square pin of a DC-DC converter: 6-ø1^±0.1 (superscripted)

An arrow pointing to a PCB pin hole for a DC-DC converter: 6-ø1.5

THe numbers almost never have measurements, but are implied to be in mm (as far as I know).

I believe it is the symbol for diameter. Google for "Geometric Dimensioning and Tolerancing"

Thanks. I had no idea what to google for which was giving me huge problems.

Yes that is what it means but is it I.D or O.D. I think it is the inside diameter

I assume it's inside diameter when it's referring to holes.

Tim Horton's (Canadian but big presence here in US) Restaurants, Dunkin Donuts and a few others actually sell donut holes. If one were specifying the diameter of a donut hole it could be kind of ambiguous - is it the ID of the hole in a donut or the OD of the resulting donut hole.

I think the heat is getting to me.