This is a wearable duffle bag that, instead of simply boosting your Carry Weight stat, acts as a portable container with a limited storage capacity – allowing you to store up to 50 lbs. of loot while itself weighing only 2 lbs.
By default, the bag can hold 50 lbs. If you try to stuff in more than the bag can hold, it won't let you, displaying a message saying that the bag can't hold any more. The bag will be auto-equipped on the player as soon as you pick it up, simulating the player slinging it over their shoulder. To use it, you must drop it onto the ground and activate it. A menu will pop up showing the maximum capacity of the bag, as well as giving you the option to Open or Take it.
Note: Weapons will be confiscated from the bag when you enter a casino, so you can't try and be clever by stuffing all your best guns inside. This applies regardless of whether you are carrying the bag or a companion is.
The maximum capacity of the bag can be modified by entering the console command
set aaaGLOBDuffleWeightMax to # where # is the weight you want the bag to be able to carry in lbs. Default value is 50.