It's a military version of a neighborhood convenience store with a gas station.
You can find here fountain drinks, canned and bottled sodas, energy drinks, beer and wine, lots of snacks, some frozen food, sandwiches as well as some sandry items for your convenience.
It has decent store hours, but it doesn't open until 10:00 on Saturdays and Sundays and closes earlier. Prices are the same as at the main post exchange, so unlike it's civilian counterpart, you don't spend extra for your convenience. That's very good. read more