|In Game Appearance|
XS-4 Armor, also known as XS, or even "shield armor" is the only armor in NotD that affects only shields rather than armor. XS-4 is also one of the lighter armors, weighing the same as C2 armor. It increases player shield capacity by 50% and adds 4 shield armor. Shield armor works identical to normal armor, but it is much harder to increase. The bonus shield capacity is based on the class's base shield value. The 20 additional shields from the CP Bonus are not added in. Medic's Nanoshield or other shield boosting abilities cast on the player are added on after calculating XS-4's shield increase. XS-4 cannot be found on Recruit Difficulty. At least 1 can be found on all other campaigns, regardless of difficulty.
Overall, the armor is best for Fortitude Demolitions. XS-4, in combination with spiked armor, high shield regeneration, and taunt, makes the Demo's shield comparable to Assault with C4. The Flamethrower is typically the second best candidate. This character has a base of 5 shield armor and a high shield pool. C4/C6 or Reactive Armor will often be favored over XS-4 by the Order Flamethrower because Righteousness does not affect shields. The Pathfinder's high shield pool and life-risking jumps also makes it a strong candidate.
XS-4 is popular among many players if it is available. It will help against unnecessary hits and ailments. Any moderate shield character such as the, Recon, Combat Engineer, or Rifleman is a fine choice. The Rifleman in particular can make good use of the armor to more easily earn a Silver Star medal.