Right now, what I am using ( kitchen Strainers ) and what stays in a 20 is what I use for 2F.
what stays in a 30 I use as for 3F.
That may not be correct, but after I get set up for a better selection of screen sizes, I may change my mind.
I don't shoot Flinters any more, so what passes thru a 30 gets re-prossed