This pack has some of the coolest hats around, and the occasional High Efficiency Battle manual. This may be your best chance to acquire these items!

Possible items you can find inside are:
Dark Randgris Helm
Judge Hat
Fish In Mouth
Observer
HE Battle Manual(3)
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Of course, due to manufacturing processes, sometimes the Kafra Gals like to put boxes inside other boxes. But, don't worry you will get your item eventually!
Tradeable and storagable.