Is it bag or a pack?
Rollover for another image. Is it a bag or a backpack? Well it's both. The REI Flash UL is sold as a generously sized stuff sack. It's large enough to pack extra clothing, lunch and cache trade items for your quick suburban and urban cache jaunts. Yet if your caching takes you deeper into the woods, this ingenious bag converts to a hydration compatible daypack simply by turning it inside out.

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DISCLAIMER: Neither the author, nor Today's Cacher magazine have any relationship with REI. The above link is not in any way sponored by REI, nor do we benefit from it.