fugensnot

I'm not sure if this has been asked before and have tried to look through each mod pack to figure out which one it may have come from. I'm referring to the second tab (denoted by the diamond armor) in your personal inventory window (accessed by pressing "E"). Could someone please tell me which mod pack this is from? What is its purpose/function? I recognize the heart canister and knapsack, but what about the other slots? Thank you for taking the time to help me.