Sienar-Jaemus Fleet Systems, abbreviated as SJFS, was a starship manufacturer that provided ships and equipment for the First Order and the Sith Eternal. The company spawned from Sienar Fleet Systems, which created SJFS to avoid New Republic arms restrictions against selling weaponry to the First Order. The presence of Sith loyalists within the executive board of Sienar-Jaemus also allowed the clandestine funneling of supplies and designs to the Final Order at Exegol through various intermediaries.
Their products included the TIE/fo and TIE/sf space superiority fighters, the latest models in the TIE fighter series produced by the company's predecessor Sienar Fleet Systems, and the Upsilon-class command shuttle. The I-a4b solar ionization reactor, L-s9.6 laser cannon, and P-s6 twin ion engine used by the TIE/fo fighter were all produced by Sienar-Jaemus as well.
The company also produced reactors, like the III-a1a primary hypermatter-annihilation reactor, used to power Resurgent-class Star Destroyers, and hyperdrive units, like the S/min-12a hyperdrive, whose projects were stolen by the Resistance and used by them for troop transports.
The databank of the Libertine, which DJ gained access to after he stole the Star Yacht in Canto Bight, contained a catalogue of starfighters for sale by the owner. It included a listing for a "Sienar-Jaemus TIE/ln," written in Aurebesh.