ah. I forgot to try to answer your original question.
You posted a link to a photo, of some foam.
If that's a (floating) closed-cell foam it looks
like a dense foam (too relatively heavy for the best dry flies).
I say that because the bubbles are big.
Big bubbles in the foam means more space between
the bubbles, where those spaces get filled by resin.
And the resin in the heavy part. The best floating
closed-cell foam has millions of tiny bubbles.
Bird shot in mason jar is heavier than buck shot
in a mason jar, because (in that case) the spaces
are the light part. But with foam it's the opposite:
the spaces between the spheres are the heavy part.

If that's a (sinking) open-cell foam, well it's hard
to tell from a photo. Softness (if soft to the touch,
and easily compressed) then it tends to be the kind
that most easily (and quickly) soaks up water and sinks
well.
Stiff open-cell foam does not soak up water well,
so it ends up floating too well for wet flies, and not
well enough for dry flies.