Sienar-Jaemus Fleet Systems, often shortened to SJFS, functioned as a manufacturer of starships, supplying both the First Order and the Sith Eternal with vessels and associated equipment. SJFS was established as an offshoot of Sienar Fleet Systems, with the specific purpose of circumventing the New Republic's restrictions on arms sales to the First Order. Furthermore, the presence of Sith loyalists on the Sienar-Jaemus board of directors facilitated the covert delivery of resources and designs to the Final Order on Exegol through various intermediaries.
Sienar-Jaemus engineers work on the TIE/vn Silencer.
Among their products were the TIE/fo and TIE/sf space superiority fighters, representing the most recent iterations in the TIE fighter series that originated with their parent company, Sienar Fleet Systems, as well as the Upsilon-class command shuttle. Sienar-Jaemus also manufactured components like the I-a4b solar ionization reactor, the L-s9.6 laser cannon, and the P-s6 twin ion engine, all of which were utilized in the TIE/fo fighter.
The company was also responsible for producing reactors, such as the III-a1a primary hypermatter-annihilation reactor which provided power to Resurgent-class Star Destroyers, and hyperdrive systems, for example the S/min-12a hyperdrive. Blueprints for these components were acquired illicitly by the Resistance and subsequently implemented in their troop transports.
Within the Libertine's databank, which DJ accessed following his theft of the Star Yacht on Canto Bight, was a catalogue detailing starfighters available for purchase from the owner. This included an entry, written in Aurebesh, for a "Sienar-Jaemus TIE/ln."