On Sun, 26 May 2013 06:06:57 +0000, Danny D wrote:

In these charts, the O-### goes up with increasing size of
the o-ring;

I should clarify that statement, by saying that for o-ring sizes
from O-001 to O-050, the designation increases as the size of the
O-ring increases.

Then the size designation jumps, to O-102, where it starts all
over again, tracking size up to O-178.

Again, there is a discontinuity, until we get to the range
of O-201 to O-284, where, again, increasing size tracks
increasing number.

Another discontinuity; and then we start at O-309 to O-395
for the next set ... until we jump to O-425 to O-475 for the
penultimate set ... and finally, we have O-901 to O-932 for
the final range.

Within a range, the o-rings increase in size with increasing
O-### designation. There are six ranges.

I'll have to dig deeper to see what the variants are that
determine the six ranges. Probably it's a ratio thing of the
key measurements to themselves.

If anyone knows offhand, why the six ranges - let us know
in a single sentence if it's not a ratio thing.