From Halopedia, the Halo wiki
Compatible with the MJOLNIR Powered Assault Armor, from Mark V to the [GEN2] platform, the FJ/PARA shoulder pauldron and knee guards were designed specifically for airborne units, with the purpose of maximum protection with minimum weight.
In 2552, Kat-B320 of NOBLE Team wore the FJ/PARA shoulder pauldrons. Four other members of NOBLE Team wore the FJ/PARA knee guards: Carter-A259, Jun-A266, Emile-A239, and Thom-A293. After the Human-Covenant War, the knee guards of NOBLE-, VIGILANT-, and Wrath-classes Mjolnir featured physical architecture similar to FJ/PARA knee guards due to the armors being recreations of the customized armors which belonged to the Spartan-IIIs from NOBLE Team. Similarly, the shoulder pauldron of INTRUDER-class Mjolnir also resembled the FJ/PARA shoulder pauldrons of Kat-B320's armor.
The FJ/PARA armor types are unlockable in the game's purchase system via the use of cR. In Halo: The Master Chief Collection, the FJ/PARA armor types are attainable in the Season 1: Noble progression system. The knee guards are unique as the only set of knee guards that are colored according to the player's secondary armor color.
Halo 5: Guardians
The FJ/PARA shoulder pauldrons are built into the INTRUDER-class Mjolnir. The FJ/PARA knee guards are built into the NOBLE-, VIGILANT-, and WRATH-classes Mjolnir variants. All these variants are unlockable in armor customization through the Requisition system.
List of appearances