Stubbs announced a Halloween 2026 skin that applies Hans Volters MKB42(H) from Killing Floor 2 to the STG-556(S). The release adds a single-piece stock whose sling slot is angled to resemble the in-game version. That stock mounts on the base STG-556, and magazines remain the standard AR15 pattern so they interchange freely. Grips attach only to the MKb-556 fire control group, which itself mounts on the STG-556.