Top panel: mean SHMFs, in units of z = 0 sub-to-host halo mass ratio, in the Symphony Milky Way suite (blue), the c125-2048 box (a higher-resolution version of Symphony Milky Way’s parent simulation) using (1) a mass-matched sample of hosts that pass the Symphony Milky Way mass and environmental cuts (solid black), and (2) the sample of Symphony target halos (dashed black), the c125-1024 box (Symphony Milky Way’s parent simulation) using the sample of 45 Symphony target hosts (dashed gray), the VSMDPL box using Symphony Milky Way’s mass and environmental cuts (green), the Caterpillar zoom-in suite (magenta), and the Caterpillar parent box (“CaterpillarParent) using a mass-matched sample of hosts that pass the Caterpillar mass and environmental cuts (solid red) and the 35 Caterpillar target host halos (dashed red). Dark (light) blue bands indicate 1σ (2σ) Poisson uncertainty on the mean Symphony zoom-in SHMF; these uncertainties are representative of other SHMFs shown that use the same (or a similar) number of hosts. Each SHMF extends down to a sub-to-host halo mass ratio of 300 particles for the lowest-mass host in each sample. Both the Symphony and Caterpillar zoom-in resolution limits are significantly below M _sub/M _host = 10⁻³. Bottom panel: same as the top panel, but for ratios of mean SHMF in Symphony relative to Caterpillar (blue), the specific Symphony host sample in c125-2048 and c125-1024 relative to the sample with only mass and environmental cuts applied (dashed black and gray, respectively), and the specific Caterpillar sample in the Caterpillar parent box relative to the sample with only mass and environmental cuts applied (dashed red).