Mountainsmith
Mountainsmith Zerk 40 Backpack
Best ultralight pack for fast-paced hikers and minimalist weekend backpackers.
The Mountainsmith Zerk 40 is an ultra-lightweight roll-top backpack designed for fast-packing, ultra-running, or weekend backpacking trips. It features a removable laser-cut framesheet for load support and EVA foam padded shoulder straps with an adjustable sternum strap. The minimalist waistbelt adds stability but can be removed. Constructed from high-tenacity recycled nylon ripstop fabrics, it offers durability and abrasion resistance. The pack has a large main compartment with a roll-top closure, an expansive front mesh pocket, angled side mesh pockets, and compression straps for secure gear lashing. Up-front mesh pockets provide easy access to essentials.
$112.95
More Zerk Options
Owner Satisfaction
4.4
/ 5
Category Rank
11036
/ 15434
#11036 in Backpacks
Price vs Category Average
+4%
Above average
Best Use
Hiking, Backpacking
/ Hiking, Backpacking
Who it's for
- Backpackers demanding long-term durability in lightweight gear
- Thru-hikers prioritizing speed and reduced physical fatigue
- Fast-moving hikers needing quick access to trail essentials
Who should skip it
- Hikers carrying heavier gear or traditional camping supplies
- Warm-weather trekkers prone to overheating on the trail
- Users requiring highly adjustable torso lengths for comfort
Performance breakdown
Weight Efficiency
Sub-two-pound construction makes this an elite choice for fast-moving hikers.
Load Stability
Removable framesheet provides necessary structure for moderate trail loads.
Accessibility
Front and side mesh pockets keep trail essentials within immediate reach.
Material Durability
High-tenacity ripstop nylon handles abrasive terrain with impressive resilience.
Carry Comfort
Wide EVA straps distribute weight well for long-distance trekking comfort.
Versatility
Modular design allows for quick transitions between minimalist and supported setups.
Key Specs
Best Use
Hiking, Backpacking
Access
Top loading
Item Dimensions
22" x 14" x 10"
Fits Torso
16" - 19"
Fits Waist
up to 48"
Frame Material
EVA Atilon frame sheet
Hydration Compatible
Yes
Item Weight
1 lb 13 oz
Know before you buy
The Zerk 40 is designed to fit torso lengths between 16 and 19 inches. If your torso measurement falls outside of this range, the pack may not sit comfortably or distribute weight effectively.
Yes, the laser-cut EVA Atilon framesheet is removable. While taking it out reduces the pack's weight, keep in mind that it also significantly decreases the structural support and load-carrying comfort of the pack.
The roll-top closure is highly versatile, allowing you to adjust the volume based on how much gear you are carrying. It provides a secure, weather-resistant seal, but you will need to ensure you have enough material to roll it at least three times to keep the main compartment fully closed.
The angled side mesh pockets are designed for easy reach, allowing you to grab water bottles or snacks without taking the pack off. However, accessibility can depend on your shoulder mobility and how tightly the pack is compressed.
The waistbelt is minimalist and intended primarily for stability rather than heavy weight transfer. It is best suited for fast-packing or lightweight setups where the majority of the weight is carried on your shoulders.
Yes, the Zerk 40 is hydration compatible. It features an internal sleeve and routing ports to accommodate most standard hydration reservoirs.
Still have a question?
Ask Hayley anything about this product before you decide.