On Sat, 25 May 2013 16:48:19 -0700, DD_BobK wrote:

Attempt to investigate trade sizes?

I have read the o-ring charts and PDFs, e.g., this chart:
http://www.allorings.com/size_cross_...nce_framed.htm

And this PDF (starting on page 7):
http://www.callapg.com/downloads/oring_catalog.pdf

In these charts, the O-### goes up with increasing size of
the o-ring; yet, in the list of O-rings I'm trying to doublecheck,
that relationship does *not* hold true.

If nobody can easily explain why, in a single sentence or so,
that means that they actually don't understand this any more
than I do.

That's OK; but for you to intimate otherwise, without
actually providing that single sentence, implies that you're
in the same boat that I'm in on this sizing discrepancy.