Named after a glacial region in Chile, the Aysén Day Pack from Nike ACG is a whole lot of bag for the price. With a durable polyester shell, the use of Dyneema® fibres give extra reinforcement that comes from innovations first developed for the sailing industry.
The roll-top design allows you to pack it down when you're not carrying too much or over-stuff it on days that you've grossly miscalculated how much junk you've got.