  The planets within compact multi-planet systems tend to have similar sizes,
masses, and orbital period ratios, like "peas in a pod". This pattern was
detected when considering planets with radii between 1 and 4 $R_\oplus$.
However, these same planets show a bimodal radius distribution, with few
planets between 1.5 and 2 $R_{\oplus}$. The smaller "super-Earths" are
consistent with being stripped rocky cores, while the larger "sub-Neptunes"
likely have gaseous H/He envelopes. Given these distinct structures, it is
worthwhile to test for intra-system uniformity separately within each category
of planets. Here, we find that the tendency for intra-system uniformity is
twice as strong when considering planets within the same size category than it
is when combining all planets together. The sub-Neptunes tend to be
$1.7^{+0.6}_{-0.3}$ times larger than the super-Earths in the same system,
corresponding to an envelope mass fraction of about 2.6% for a $5\,M_{\oplus}$
planet. For the sub-Neptunes, the low-metallicity stars are found to have
planets with more equal sizes, with modest statistical significance ($p\sim
0.005$). There is also a modest $(\sim$2-$\sigma)$ tendency for wider-orbiting
planets to be larger, even within the same size category.
