As I mentioned before, and before, there is a "funnel shaped ramp" inside the fitting that the hose must fit, in order to create the seal. It will not seal on brass or aluminum, as the material must "form fit" itself into the seal area to create the seal. The elastic properties of polyurethane and other formulations of plastic hose/tubing is what allows this "conformal seal" to be accomplished. A flexible ring of fingers with action similar to a "Belleville Washer" retains the tubing by spring pressure. Depressing the blue colored collar flexes the spring loaded fingers and disengages them from the surface of the hose/tubing, allowing extraction.

Brass and/or aluminum tubing is not malleable enough to be formed into the required shape with just finger pressure.

Why bother chancing a leak by shoving brass tubing into a Festo fitting when numerous easily located, readily available, less leak prone, inexpensive fittings exist?
The incorrect use of some parts, like a Festo fitting, in the manner for which it was never intended, could have a dangerous and expensive outcome.
I just don't want some "newbie" to use this type of idea and have some unexpected, fiery consequences.
Either type of leak, suction or pressure, can ruin your day.

Nope, I don't have any metric brass.

Harley Condra
BVM REP
JetCat REP