On Sunday, 6 December 2020 at 17:24:31 UTC, Dave Plowman (News) wrote:
...do the AF nut sizes on 15mm compression fittings vary by so much? About
1.5mm between the smallest and largest here. All new. The threads seem the
same - you can interchange the nuts.

If space is tight, you need a good spanner fit. And I hate adjustables.

Agreed - it seems odd that no-one seemed to define a standard. Or if they did, it didn't stick.