If super lightweight walking or ski touring is the thing for you then the Mont Helium 600 down sleeping bag is an ideal choice. Impressively light, surprisingly compact and exceptionally warm by way of 800+ loft down.
Mont Adventure Equipment says:

The Helium 600 is suitable for temperatures as low as 14F and still weighs 2lbs! Ideally suited to cold weather and four season camping including use above the snowline.
Ultralight shell fabric and high-loft down fill on the Helium bags mean higher performance for less weight. Durable 10 by 10 denier, 520 thread count Nylon weighing only 26g/m2 with a hot-rolled-cire treatment to prevent down leakage and increase durability. Premium 800+ loft RDS white down fill with DWR Loft treatment adds greater resilience, higher loft and better warmth in damp conditions.
If youre heavy on experience youre better placed to travel a little lighter. Light on skills and light on gear decreases your safety margin.Mont Ambassador and backcountry guide Doug Chatten. While the Helium 600 is rated to 14F, it is not appropriate for alpine snow camping unless you’re an experienced alpinist.

Our Verdict
Mont Adventure Equipment is an Australian company known for making high-performance gear for demanding alpine conditions, with a focus on low weight, precise design, and reliable materials. The Helium 600 LHZ Down Sleeping Bag is a clear example of that design philosophy.
Weighing 995g, the Helium 600 provides dependable warmth for cold three-season or shoulder-season use. The 800+ loft down is treated to retain loft in damp air, and the shell fabric feels well-engineered for its weight. It packs down to 16 33cm and lofts quickly on release. The fit is generous enough for extra layers or a liner, with a tapered rectangular shape that doesn’t feel restrictive.
Vertical torso baffles and box-wall construction help keep insulation stable across the upper body, while a well-shaped hood and large draft tube improve thermal retention. The breathability holds up well in changeable conditions. The full-length side zip is practical for venting, although it can catch if not handled with care.
For extended trips in cooler, damp environments, this bag offers a solid warmth-to-weight ratio with thoughtful construction and a strong record of performance.
– Reviewed by Ultralight Outdoor Gear

Features

Tapered rectangular shape with a wide foot section for room to move
Radial Arc Baffle System on horizontal baffles maximises loft height & warmth
Vertical baffles on torso maintain optimal down distribution
Differential cut reduces compression & cold spots
Box walled baffles for warmth & weight efficiency
Large down-filled 3D draft tube along zip retains heat
Contoured hood keeps down evenly distributed around head
Laminated 210 denier Nylon anti-snag shield along zips
Sewn with hydrophobic Epic thread to prevent moisture from wicking along seams and inside the shell
Tuck stitched for seam strength & greater water resistance
Full length YKK side zip with dual sliders & foot zip
Includes ultralight siliconised-Nylon Z-Force Mechanical Advantage Compression Stuff Sack & 50L / 3,051cu. inpolyester storage sack with printed care & washing instructions

Specifications

Regular Weight: 995g
Long Weight: 1147g
Compression Sack Weighs: 103g
Cold Sleeper: 25F / -4C
Warm Sleeper: 14F / -10C
Season Rating: 4 Season
Packed size: 6.3×12.9 inches (16x33cm)

Material & Construction

Shell fabric 520 thread count, 10 by 10 denier ultralight Nylon (26g/m2)
Lining fabric 520 thread count, 10 by 10 denier ultralight Nylon (26g/m2)
Down rating 800+ loft premium RDS white duck down
Down treatment Water resistant DWR Loft treatment
Zip side: Right Regular, Left Large
Zip configuration Side & Foot zips. YKK brand zips, dual sliders on side zip
Colour Orange/Black

Help & advice:

How to Wash and Care for Your Do