For my PSK I just keep them in a mini-altoids tin (both practical and amusing), but for my FAK I've taken one of those 7 day pill containers and printed up labels for each compartment outlining what the pills are, what it's for, the dosage, and expiration date.
For example, one reads:
Ranitidine
Acid Reducer
75mg
2008 MR
...Since my kit itself is sufficiently water-tight, it works quite nicely.
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When you step out that door in the morning you never really know what you're going to encounter.