Yes, we wanted to have 2 levels of protection against leaking. The first is the interference of the tapered surfaces against each other on the tip of the AN union/fitting. The secondary is an O ring that gets the proper amount of compression by the same fitting's hexed flange.
Later
"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut." - Albert Einstein
When was the last time you *really* did something with your Z to call yourself a Z enthusiast?