What paramedicpete said - make sure you have training to use everything, particularly the tourniquet and chest seal.

I do pack a bag with rolls and rolls of kerlix, lots of 4x4s, some 4x6 ab pads, gloves, and about 10 rolls of adhesive tape - its EDC in the sense its in my car every day, and another at home every day, and a third in my office every day, so 'it' goes in proximity to everywhere I go but is not 'on my person' every day. If my building collapses the kit is stuck with me - if another building falls down, I'm there with 1 or even 2 kits, assuming I stop at my car. Also some triage tags, scissors, some splint material on the bottom, some cheap rain ponchos, some essentials I'm forgetting, but basically its all meant to stop bleeding and control shock for a period of time (less than 24hrs).

Same kit contents, three copies. I can treat one person, or 50-75 people from each bag. Another person who needs supplies can pull from this bag. I can apply only the level of care I'm trained for by nature of the contents. I have one tourniquet and one Asherman's chest seal per bag, and about 2 hours of formal training in their application, which I think is pretty minimal, mostly limited to identifying situations when you definitely would need to apply them. I am not likely to take the time to apply either in a mass casualty situation, but a trained EMT might.

In the course of the last year I have pulled some kerlix and some 4x4s from this kit for isolated injuries. I have added a small supply of knuckle band aids and some neosporin just because I can find them easier in this kit than unpacking my regular FAK. The contents are all durable, nothing slated to expire, so its a sunk cost I've invested in Just in Case.