The 2-liter Source reservoir has a 6-inch-wide mouth for easy filling and a bite valve cover that keeps dirt out. We wish all hydration packs had this latter feature.
A distinctive shock-cord system glues this pack tight to the body: Dual sternum straps crank down on the upper and lower torso; another set of cords runs from the lower shoulder straps to the packbag.
Two long, mesh shoulder-strap pockets keep snacks or a phone at the ready; a bungee on the front secures a helmet.
The glued-on fit leaves little room for airflow (a tradeoff for superior stability).