From Gear Patrol:

“The backcountry is the absolute worst place for gear to fail, and an adventurer’s pack — carrying the most valuable resources — can never, not even for a moment, falter. The proper water-resistant daypack is small and agile, bereft of extraneous detail. It should also be designed to minimize the chances of something falling out, tearing off or breaking loose. The gear you carry isn’t much use 50 feet down a cliff. These five daypacks will let you tackle all the ruggedness of the backcountry — and still come out unscathed.” 

Read more here.