We would never suggest you limit yourself to just one pack. But if you can't fit more than one in your tiny Manhattan flat, the folks at Osprey feel your painand have the solution. The Aether is light enoughand its ventilated back panel cool enoughfor a quick summer weekend on the steamy Appalachian Trail. Come October, it has the capacity and weight-bearing ability to handle a week in the Rockies. The heat-moldable hipbelt is a little gimmicky, but it's one of the most comfortable you'll find, even if you don't bake it in the oven (at the store, not at home). 3.9 lbs, 3,700 cu in; www.ospreypacks.comBonus: The tough pack bagwith its cavernous lid pocket, stretch-woven sleeves on sides and front, multiple lashing options, and a deep divot for head clearanceis one of the best we've seen.Bummer: The Aether's tall profile can make it a bit unstable if not packed carefully.