Expansion Box S is used to upgrade your base warehouse (vault) storage. You don’t “open” or equip it. It’s a required material for specific vault upgrade tiers, and it’s consumed when you apply that upgrade.

Use Expansion Box S at the warehouse (step by step)

  • Make sure the Expansion Box S is in your character inventory when you return to base.
  • At the hideout, go to the first NPC (Jeff). Interact with the main storage locker behind him.
  • Open the storage UI and switch to the storage upgrade screen. On PC, use the on‑screen tab switcher (mouse wheel) to move to the Storage Expansion/Upgrade Vault tab.
  • Select the next available vault upgrade tier. Early tiers may only cost credits; later tiers add item requirements like Expansion Box S, then M and L.
  • Confirm the upgrade. The box and required credits are consumed, and your warehouse capacity increases immediately.
Note: You must carry the box on your character for it to count toward the requirement. Placing it in storage before upgrading can prevent it from being detected by the upgrade screen.

Where to find Expansion Box S (and a fast early route)

Expansion Box S can drop very early. Players regularly find S and M in lockers in the first area. A quick loop that works well: enter the first area, go northwest through the portal, then continue upward; sweep lockers along the path and extract. This keeps risk low and focuses on high‑yield containers.

Toolboxes across regions also have a strong chance to spawn expansion crates. Crate drops are RNG‑gated, so expect a few empty runs between hits.

Tip: Larger crates (M and especially L) are heavier. If you’re carrying one, prioritize extraction to avoid losing it.

What Expansion Box S actually upgrades

Expansion boxes only increase warehouse capacity at your hideout. They don’t add slots to your mission loadout or backpack. Vault upgrades unlock in tiers, each granting more storage space; later tiers add item requirements (S → M → L) alongside credits.

Credits can be earned quickly by offloading surplus loot at vending machines in the base. If you’re blocked by a credit requirement, liquidate non‑essentials, then return to the upgrade screen.

Backpack capacity is separate

If you’re trying to carry more during raids, Expansion Box S won’t help. Backpack capacity scales through:

  • The Skill Enhancement machine at your base (choose the Backpack Expert upgrade line; higher ranks may also require items).
  • Finding specific backpacks in the field that permanently add slots when used.
  • Body armor pieces that increase carry capacity.

These systems are independent of the warehouse. Upgrade both tracks to smooth out your loot flow: backpack for runs, warehouse for long‑term storage.

Expansion crate types and what to expect

Item Used for Common places Notes
Expansion Box S Early vault tiers that require items First area lockers; toolboxes anywhere Lightest crate; shows up early
Expansion Box M Mid vault tiers First area lockers (rarer); toolboxes Heavier than S; plan your extract
Expansion Box L Late vault tiers Toolboxes and high‑value caches Heaviest; expect fewer spawns

If the upgrade screen won’t accept your box

  • Move the box from storage to your on‑character inventory and reopen the upgrade tab.
  • Check that you’re on the Storage Expansion/Upgrade Vault tab, not the regular storage view.
  • Confirm the tier you’re selecting actually lists Expansion Box S. Some earlier tiers don’t need it.
  • Ensure you have the required credits alongside the box.

The short version: carry Expansion Box S back to base, open the locker behind Jeff, switch to the storage expansion tab, and apply the upgrade tier that lists Box S. For steady farming, run early‑area lockers and toolboxes, then extract as soon as you snag one.