I bought this for a planned hiking trip in New Zealand (Milford Trek) which spans 33 miles over 5 days. Leaving in just over 2 weeks, so I have packed this thing to the brim and although there isn?t a lot of extra space, I have jam packed in all I hope I?ll need for the trip. I choose a smaller backpack, because on the longest day of our hike, we?ll be traversing 14 miles and I?d prefer to keep it as light as possible. There isn?t room for a sleeping bag and what not (which for this organized trek we travel between hotels), but for me I squeezed in a backpack rain cover, 8 Smartwool PHD socks (4 boot and 4 low-profile) and 8 sock liners, NTS base layer lightweight top and bottoms, PHD HyFi full zip jacket, 5 non-cotton t-shirts (U.A. Catalyst, TNF Reaxion and Flex Crew), Outdoor Research Crocodile Gaiters, NEOS Trekker OverShoes, TNF Venture Jacket and Side-Zip pants, CamelBak 100 oz water reservoir & a spare pair of Salomon 3D Ultra 2 GTX low-profile shoes in the bottom of the bag ? plus all the other accessories (international adapters, LifeProof iPhone 5 cover, undies ? toilettes etc). I was able to squeeze this stuff in by using these compression zip-lock bags I found buried in my closet. Squeeze all the air out and things pack better then you?d expect!