Mountain Equipment Helium 400 Sleeping Bag (-5°C/23°F)

An exceptionally lightweight, versatile, and easily packable sleeping bag, ideal for backpacking, mountaineering, and cycle touring. The Helium 400 proves a dependable companion for cooler nights during spring and summer adventures.

Filled with 403g of responsibly sourced, minimum 700-fill power duck down (DOWN CODEX-approved) and wrapped in a high-performance 100% recycled Helium 20D outer shell, the Helium 400 delivers excellent warmth, minimal weight, and impressive compressibility for hassle-free packing. Its streamlined shape offers both comfort and efficiency, making it a top choice for those seeking low weight without sacrificing warmth during colder nights.

The slanted baffle construction across the body ensures down stays in place, maintaining consistent insulation and boosting packability while eliminating cold spots. At the foot of the bag, a four-baffle layout concentrates warmth precisely where it's needed, and in the hood, a five-baffle design ensures the down remains evenly distributed for optimal comfort and thermal performance.

Inside, the bag features a 100% recycled Supersoft 20D lining treated with a PFAS-free DWR for breathability, durability, and a comfortable night’s sleep. A full-length Gemini™ zip baffle, carefully engineered with a stiffened structure, prevents heat from escaping and avoids snagging. The Lode Lock™ magnetic closure and adjustable collar drawcords provide easy handling, even in low light or cold conditions.

Crafted with the technical yet comfortable Alpine 2.0 fit, the Helium series offers enhanced thermal efficiency while keeping the weight to a minimum. With a Good Night’s Sleep Temperature of -5°C (23°F), the Helium 400 is ready for journeys to colder northern regions and high-altitude adventures in early spring or autumn.

Features

Insulation

• The baffle structure has been precisely optimised to achieve the best possible warmth-to-weight ratio.
• The Regular version contains 367g of 90/10 duck down with 700+ fill power.
• The Long version includes 388g of 90/10 duck down with 700+ fill power.
• All down is ethically sourced under the DOWN CODEX© and RDS 3.0 standards.
• Each sleeping bag is accompanied by a unique DOWN CODEX© code, ensuring full transparency on both sourcing and fill power.

Materials

• The recycled HELIUM™ 20D outer fabric is a lightweight 38gsm material that expertly balances durability, compressibility, and resistance to the elements. It is tightly woven to fend off wind and minimise heat loss, and it features a PFAS-free DWR coating.
• The Supersoft™ lining is crafted from 38gsm 20D recycled downproof nylon, designed for breathability, longevity, and a soft touch against the skin, also finished with a PFAS-free DWR.

Patterning & Design

• Engineered with longevity and high performance in mind.
• The Women’s Alpine Fit showcases a carefully tapered profile enhanced by a zoned EXL® system to improve thermal efficiency while trimming excess weight.
• Slanted box-wall baffles help reduce structural mass while maximising insulation performance.
• Strategic fill placement ensures higher density insulation in critical areas such as the underside, hood, and foot box, helping prevent down migration and keeping warmth exactly where it's needed.

Foot box

• The Trapezium 4 System employs a four-baffle construction that maintains insulation around the feet and prevents compression, delivering toasty toes throughout the night.

Hood

• Features a five-baffle design for meticulous down control, minimal weight, and outstanding insulation.
• Shaped to be roomy yet secure, with dual tether drawcords that minimise heat loss efficiently.

Zip Baffles & Collars

• The Gemini™ Baffle System presents a lightweight, low-profile design that combats heat loss without compromising protection.
• The Lode Lock™ System offers a dependable magnetic closure with a mechanical lock, allowing for quick one-handed operation.
• An integrated and adjustable down-filled neck collar enhances warmth and comfort further.

Additional Features

• A waterproof roll-top stuff sack is included, helping to save pack space while keeping the bag dry in damp conditions.
• Comes with a Storage Cube to maintain loft and improve long-term performance, making it ideal for home storage.
  
  

Specifications

Technology

	Down 700 Down is the finest insulator that we have. Its warmth to weight ratio, compressibility, long lifespan, and softness are yet to be matched by manmade insulations. For all but the most serious expeditions, duck down is a great choice for both insulated clothing and equipment.
	Helium Helium fabrics are exceptionally light, compressible and soft. Their densely woven construction ensures the highest levels of down-proofing and wind resistance.
	Down Codex® The DOWN CODEX® is our multi-award-winning certification scheme that considers the environmental, ethical and animal welfare matters relating to our down supply chains. It is grounded in comprehensive and transparent auditing that ensures traceability and quality.
	Fair Wear As a member of Fair Wear, Mountain Equipment is committed to implementing the highest standards of working conditions. Mountain Equipment were awarded 'Leader Status' by Fair Wear Foundation in 2016 and has been awarded their highest accolade for performance every year since.

Detail Shots

	Using slanted box-wall baffles throughout the entire main body of the helium bags means weight is removed from the bags structure, yet they remain a significant step above a standard box baffle.
	5 baffle anatomically shaped hood.
	4 baffle anatomically shaped and offset foot-box.
	Full length Gemini zip baffle with 140cm zip and integrated neck collar with Lode Lock closure.
	100% recycled HELIUM 20D outer shell is very light and highly breathable with PFC free DWR.
	Integrated neck collar with Lode Lock closure.

More Information

Helium Sleeping Bags

Efficiently sized, supremely comfortable and low in weight each Helium bag offers outstanding all-round performance for backpackers, cycle-tourers and trekkers. These bags don’t skimp on features and will keep you warm and comfortable whether on a summer road-trip or extended trek.

Shop The Helium Range