Question re tube size nomenclature

[mainemandean]

My System One 560 machine has settings for two different tube sizes. The choices are 15 and 22.

I am confused, because it seems to me that tubes come in two varieties:
15mm ID, and
19mm ID.
And both of the above come with collars that have a 22mm ID.

I think that since I am using the 19/22 hose (as opposed to the 15/22 hose), I probably should use the "22" setting, because bigger hose would seem to dictate the bigger (higher) number.

I can't be sure, though, because to me the size designations don't make sense.

What say ye?

[Sleeprider]

Use the 22 mm setting unless you have the Slim-Line tube sold as 15 mm or the heated tube, which will automatically set.

[SarcasticDave94]

Good answer there. And the survey says he's right.

[mainemandean]

Thanks, folks.