The 5L Aux Pox (V2) mounts on the back and/or front of the Backcountry 35 Pannier, using 5 bolts, washers, and tee nuts. It consists of a harness and a removable, welded-seam, roll-top drybag. The harness can also be used without the included drybag, for things like fuel bottles, a hydration reservoir, or a tool roll. The V2 features velcro closure hatch door for the MSR dromedary nozzle at the bottom of the harness. There's Hypalon armor along the bottom to the edge to protect against abrasion and reflective panels on the outer face for visibility.

Each individual Backcountry Pannier can fit up to three Aux Pox: one on the front, one on the rear, and one on the bottom. Or you can remove the Aux Pox entirely for a more minimalist fit.