OK, this is one of those ridiculous questions, but why don't some 12 AN fittings (Aeroquip) fit 12AN wrenches?
The fittings are 12AN and are too small for a 12AN wrench and too big for a 10AN wrench and of course they don't make an 11. I know they make adjustable alloy wrenches, but WTF?

__________________
“There are only three sports: bullfighting, motor racing, and mountaineering; all the rest are merely games.”
www.partskeeper.com
(Less time searching, more time wrenching & driving)