Which size drain pipe for yoke columns in USA?

We have have 2 inch and three inch diameter drain pipe in the USA. This spec refers to the inner diameter. Most of the articles on yoke building refer to 80mm pipe. 80mm is very close to 3 inches, but that may refer to the outer diameter. In photos, the "80mm" pipe looks smaller than US 3" pipe. US 2 inch pipe looks too small. 3 inch, huge and out of scale. I am wondering what the real size is of Boeing yoke columns and which is closer to the real thing. What do US builders typically use? I can't imagine Boeing using metric anything on purpose.

Silly question, but I'm sure it's come up before. Thanks for the help.

Should be 70mm external, 60 mm internal as far as I know.