  We study reduced products $M=\prod_n M_n/\mathrm{Fin}$ of countable
structures in a countable language associated with the Fr\'echet ideal. We
prove that such $M$ is $2^{\aleph_0}$-saturated if its theory is stable and not
$\aleph_2$-saturated otherwise (regardless of whether the Continuum Hypothesis
holds). This implies that $M$ is isomorphic to an ultrapower (associated with
an ultrafilter on $\mathbb N$) if its theory is stable, even if the CH fails.
We also improve a result of Farah and Shelah and prove that there is a forcing
extension in which such reduced product $M$ is isomorphic to an ultrapower if
and only if the theory of $M$ is stable. All of these conclusions apply for
reduced products associated with $F_\sigma$ ideals or more general layered
ideals. We also prove that a reduced product associated with the asymptotic
density zero ideal $\mathcal Z_0$, or any other analytic P-ideal that is not
$F_\sigma$, is not even $\aleph_1$-saturated if its theory is unstable.
