The Attache Case, functions as part of the player's inventory screen in Resident Evil 4. It consists of a grid on which items snap into place; the items can be moved and rotated to fit the player's liking. The case is only for weapons, weapon attachments, ammo, and health items with the exception for Ada in Assignment: Ada who has to use space for Plaga Samples which are key items.
The case is initially quite small, but the player has the option to buy larger cases from the Merchant over the course of the game.
Leon and Ada's Case at the start of Resident Evil 4, This version has minimal room for the player to keep items (ammunition, healing, etc.) unlike the medium, large or extra-large versions for sale from the merchant.
Specifically, the inventory space of the Attache Case S is ten by six squares for a total of sixty squares.
It is not required to upgrade to the medium size to be able to purchase the large and so on - it's fine to wait and save a bit of money (the medium only adds one row and one columns).
Attache Case M
"A medium size case. 7x11 (77 boxes)"
Upgrading from the small case to the medium case adds one row and one column to the inventory. The total inventory space of the Attache Case M is eleven by seven squares, or seventy-seven squares total, a 28% increase.
Attache Case L
"A large size case. 8x12 (96 boxes)"
The Attach Case L expands the medium case by one row and one column. Its inventory space is twelve by eight squares, or ninety-six total squares, a 24% increase from the medium case and a 60% increase from the small case.
Attache Case XL
"The largest case available. 8x15 (120 boxes)"
Buying the XL case adds three columns to the inventory grid for a grand total of one hundred twenty squares, exactly double the space that Leon had at the start of the game.
There is a Rocket Launcher in the room before the Merchant that sells the Attache Case XL. If you buy it right there, the Rocket Launcher easily fits in the new case.
Main Game and Separate Ways Cases
|Available for Leon||Available for Ada||Price||Dimensions||Size|
|Default Case||---||---||---||6x10||60 boxes|
|Attache Case M||Chapter 1-2||Chapter 2||24000₧||7x11||77 boxes|
|Attache Case L||Chapter 3-1||Chapter 3||40000₧||8x12||96 boxes|
|Attache Case XL||Chapter 3-3||Chapter 5||73000₧||8x15||120 boxes|