Mountainsmith
Mountainsmith Zerk 55 UL
With the Scream 55 gone, the Zerk 55 UL is the only current 55 L pack in Mountainsmith's range, the larger-volume version of its 2026 roll-top Zerk update. It holds 53 L, or 58 L with the roll top extended, on a removable EVA/Atilon frame sheet rated for a suggested 40 lb. At 3 lb 8 oz it is heavier than most packs sold as ultralight, so it suits hikers who want a burly fabric and a sheet frame more than a minimal gram count.
Specifications
What do these specs mean? →Features
Pros
- ✓Robic nylon with an Extreema UHMWPE grid and a 210D base is tougher than the thin fabrics most 50-plus litre UL packs use.
- ✓Suggested 40 lb load, with Mountainsmith stating it tolerates 25% more, gives real headroom for food and water carries.
- ✓The interior was re-patterned to take some 700 cubic inch bear canisters.
- ✓Two zippered hipbelt pockets and a hydration sleeve with hose port come standard.
- ✓Two torso sizes and a 28-48 in waistbelt cover a wide range of hikers.
- ✓The frame sheet is removable, so the pack can be stripped down for lighter trips.
Cons
- ✗3 lb 8 oz is heavy for the ultralight label; carbon-stay competitors of similar volume weigh closer to 2 lbs.
- ✗Bear-canister fit is hedged to 'some makes', so check your canister's dimensions first.
- ✗No lid; the optional 7 L Toplid is a $34.95 accessory.
- ✗No raincover and no ventilated back panel.
- ✗Torso length is fixed within each size rather than adjustable.
Compare the Mountainsmith Zerk 55 UL
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