The backpack in Fallout 76 serves a precious function in that it can increase your carry weight. In addition, you can add Mods to it to provide additional benefits to your character. One of those mods, The Chemist's Backpack Mod, reduces the weight of all Chems by 90%. However, this Mod does not stack with other Perks that provide the same benefit. Still, this Mod is invaluable, primarily if your character uses a build that thrives on using Chems, which will save you valuable carrying weight. Here's where to get the Chemist Backpack Mod in Fallout 76 and how to apply it.