Ahh ok. You can find out the gpd from the membrane inside the housing, just take it out and read what it says.
That should give you at least an idea of what the unit is capable of.
I have a psi meter built into my ro
so I can see when the pressure drops from clogged filters. i also have mine hooked up to a garden hose spigot which might explain the high water pressure I have. Not sure if you can buy a handheld meter, probably.