Sierra Designs Flex Capacitor 40-60L Backpack

No, you might not be able to travel through time using this pack, but there's a good chance it's a gift from the future. The Sierra Designs Flex Capacitor Backpack can expand and compress throughout your trip as your needs change, and it does so with lightweight stability. A unique gusset system on the back lets you enlarge the bag to 60 liters at the start of your trip, then tighten it down to 40 liters as your food reserves dwindle and you've moved layers from bag to body. Whether your trip last two days or seven, you'll be glad for all the places to stash your stuff, thanks to seven different pockets as well as loops on the back for your ice axe. If you're trekking through uneven terrain or might encounter snow, the compression straps can help keep the necessary tools attached, waiting and ready for deployment. A zippered stash on the top of the bag is a perfect hiding place for the vitals you'll need throughout the day, and there's even a spot for your reservoir should you get thirsty.

Price: $199.95 from Backcountry