I'm not a commuter.
I ride my bike in the mornings and afternoons, and sometimes have to "take a break between rides" to work...but I'm not a "commuter."
So I did not want a bag that looked like one.
Waterproof: Check. Low profile: Check. Sleek, Castelli branding, waterproof zippers, functional pockets, and the best darn compression and suspension system of any pack this side of alpine ascents: check, check, and check again.
The shoulder straps perfectly cradle the upper shoulders and neck, so you know its a bag made for racers. Its not a casual fit by any means, so expect it to be snug around the upper. Its meant for riding in an aggressive position. The tuck away feature at the back allows extra straps to be neatly hidden away behind the back, and the airflow through the ventilated back panels is outstanding. The zippers, while thick, strong, and waterproof, have amazingly stable and smooth action, and the seal is fantastic. So good in fact, that this pack went from my daily Commuter...err..."riding bag"...to my go-to theme park hauler. Not only did it hold a plethora of various child-silencing snacks and liquids, but it resisted the spit of Harry Potter Spiders, Giant genetic dinosaurs, and inebriated animatronic Pirates. Not a drop of re-circulated ride water infiltrated its sleek black walls...all the while, sending the cool, quiet message to the masses lined up behind that this was a piece of racing gear, not just a cycling backpack.
Well done Castelli...well done.