Mountainsmith

Zerk 40L Backpack

What Our Gearhead® Experts Are Saying:

"I’ve put real mileage on the ZERK 40, and the shoulder strap system is the star here. Even loaded for a multi-day, the pack stays close to the body, and those front pockets make hydration and snacks way easier to manage in motion."

Multi-day miles require steady organization, and the Zerk 40L Backpack from Mountainsmith is tuned for the balance between load capacity and efficient movement. The roll-top main compartment stores up to 40 liters of gear, with an additional 4 liters in the top area when expansion is needed. Throughout the exterior, modular compression straps secure layers, pads, or wet items without interrupting access to the core storage zone.

Dual angled bottle pockets promote quick hydration, while four front-strap pockets keep essentials—gels, bear spray, filters, or soft flasks—available without breaking rhythm. The expansive stretch mesh panel holds bulky or damp items, and reflective webbing maintains visibility on pre-dawn starts or late finishes. EVA-padded shoulder straps support the torso through long climbs and shifting ground, aided by adjustable sternum straps that refine the fit as terrain steepens.

Ready for long hauls and built for technical, variable environments, the ZERK 40 accommodates the full kit without sacrificing agility on the move.