Developed as a replacement for the MG15 machine gun, the MG81 was intended for use as aircraft armament in flexible mounts, both as individual weapons an in the "MG81Z" twin mount configuration. The MG81Z was installed in many German aircraft in the intended flex mount role, along with being used in fixed rear-firing defensive mounts on the Do217 bomber and used in the ground attack role by putting three MG81Zs in a gun pod (six total machine guns per pod) for strafing attacks. The 81s in this lot share a swiveling mounting bracket attached to the heat shields and a spade grip unit with extended trigger levers mounted at the rear (the aforementioned apparatus is all professionally modern made). Unlike the more common MG34 and MG42 machine guns, the recoil springs are set inside the main body of the receiver, and the feed mechanisms are mirrored, with a swiveling feed chute on each side and a belt link chute running from the interior back out to the sides. Each has a top cover bearing the "MG81" nomenclature, "byf" (Mauser) manufacturer code, Krieghoff proofs and numbers "32175a" and "32176a" respectively. The Krieghoff proofed receivers are also sequentially numbered "11231a" and "11232a", with steel cable pull-cord charging handles and unified trigger housing with push-through safety.

As described in A.