Seeker wrote:

....
...Harbor Freight is an excellent place for high flow air fittings. I believe HD,
Lowes have a limited selection too.

I've never used HF's fittings so have no idea what they're like or
whether they are consistent. There's a "veritable plethora" of
differing designs which are not all interchangeable, even for the same
nominal size(s). I suggest standardizing on a name manufacturer such as
Milton of a given style so you're not dependent on the "stock of the
day" at the Borg or other vendor...