Part of smersh vest set. It’s not the biggest backpack ever, but you can attach it to the vest and keep a place for an additional backpack.
The Smersh Backpack is a small-sized backpack.
The Smersh Backpack has as many slots as a UK assault vest, but can be attached to the Smersh Vest to add additional capacity into your inventory. You can also take another backpack on your back after you have combined the two.