First and foremost - your Expedition Backpack needs to be big enough to carry all the food, water, and gear you'll need for trips lasting a week or longer AND comfortable enough so that you actually enjoy your adventure. Expedition Backpacks are usually between 80 and 115 liters (5000 - 7000 cu in) of capacity. Consider what your trip will look like - are you through-hiking the Pacific Crest Trail? Or are you hiking up Mt Katahdin with lots of day trips from a base camp? Our backpack experts here at CCOutdoorStore.com can help you decide the best expedition pack to buy. Whether a pack with large internal volume is best or a backpack with the ability to strap on a lot of gear - our experts will help you shop for your pack and give you advice on Ultra-Light tents and sleeping bags too. Just give us a call 855-244-GEAR if you need advice.