Most important of all is the suspension system, check out the suspension system on the camp-trails link. I have an adjustable torso on my pack, wear it in the store with some weight on it, try to step up and down steps with it on, check out shifting, bouncing and strain on you back. The belt should be snug over your hips, should straps start at the nape of you neck but over on your blades a little. chest strap should be mid pecs. I would never buy a pack without trying it on and testing some of these things. If you are odering from the internet, see if there is someone (tradgang) member with a pack in your are so you can try it first.