Air Fittings

A lot of this can also depend on.............

Whether your compressor runs "towards high" or "towards low" on the pressure end, or sags a lot before the switch cuts in

Whether your hose is real true 3/8 or some of the cheap stuff is actually closer to 5/16. And, the internal hose liner if it's rough can matter.

AND HOW LONG your hoses are

Of course the size of piping, if it's marginal. There are some commercial "piping" kits out that use proprietary non metallic piping that is quite small ID

I have a big ol HUGE I/R 3/4 impact that comes out when something is really really tight, and for that I've got enough 1/2" HALF inch hose to reach from the garage to the front street!!. I often use a piece of it with a shorter length of 3/8 from there to the tool On a tool that is an air hog, or an impact, it can make a difference.

Most of my couplers are old Hansen Milton 1/4" the stuff for the 1/2" hose and 3/4 impact is larger