Mountain Equipment Helium 400 Women's Sleeping Bag (-5°C \ 23°F)

An exceptionally light, highly versatile and easily packable sleeping bag, the Helium 400 is tailored for those venturing into backpacking, mountaineering, or cycle touring. It comfortably handles chillier conditions during spring and summer nights with dependable warmth.

With 403g of ethically sourced duck down boasting a minimum 700-fill power and certified by DOWN CODEX, this sleeping bag is matched with a high-performance Helium 20D outer shell made entirely from recycled materials. The result is a sleeping system that is impressively warm, featherlight, and compressible enough to tuck away with ease. Its trim yet comfortable fit makes it ideal for weight-conscious adventurers, providing sufficient insulation for cool-weather overnights.

The slanted baffle design along the body ensures warmth is maximised by evenly distributing insulation, eliminating cold spots and boosting packability. The foot box benefits from a four-baffle arrangement, delivering targeted warmth to the lower extremities. Meanwhile, the hood employs a five-baffle configuration to ensure the down stays exactly where needed for consistent comfort through the night.

Inside, the bag is lined with Supersoft 20D recycled fabric, treated with a PFAS-free DWR for breathability, resilience, and enduring comfort. A full-length Gemini™ baffle runs alongside the main zip, virtually sealing off any escape routes for heat. This feature is stiffened to prevent snagging. The Lode Lock™ magnetic closure system, paired with intuitive collar drawcords, offers simple operation even in complete darkness.

Crafted with the technical Alpine 2.0 fit, the Helium 400 blends ergonomic comfort with thermal efficiency. Its Good Night’s Sleep Temperature rating of -5°C (23°F) makes it a reliable companion for adventures in cooler northern climates, as well as early spring and autumn forays at elevation.

Features

Insulation

• Each baffle is optimally filled to maximise the warmth-to-weight balance.
• The Regular size contains 261g of 90/10 duck down with a fill power exceeding 700.
• The Long size includes 273g of 90/10 duck down with a fill power exceeding 700.
• The down is ethically gathered under the DOWN CODEX© and RDS 3.0 standards.
• Every Helium 400 bag is supplied with a unique DOWN CODEX© ID for full traceability of origin and fill quality.

Materials

• The outer fabric is crafted from Recycled HELIUM™ 20D, a 38gsm, 20-denier recycled material that offers a balance of lightness, durability, compressibility, and resistance to the elements. It is tightly woven to block wind and retain warmth and finished with a PFAS-free DWR.
• The interior lining is Supersoft™ 20D recycled downproof nylon, designed to be breathable and gentle against the skin, while maintaining strength and treated with a PFAS-free DWR.

Patterning & Design

• The design is engineered for lasting durability and peak performance in challenging conditions.The Women’s Alpine Fit features a tapered profile with a zoned EXL® system that boosts thermal efficiency while keeping overall weight to a minimum.
• Slanted box-wall baffles help trim structural weight and fine-tune insulation placement.
• Down fill is strategically concentrated in critical zones such as the underside, hood, and foot area to minimise migration and maintain warmth where it's needed most.

Foot Box

• The Trapezium 4 System uses a four-baffle layout to preserve loft, prevent cold spots, and keep feet warm without restricting movement.

Hood

• A five-baffle structure ensures excellent down distribution, efficient insulation, and a low weight.
• It is shaped to be both spacious and secure, with dual tether drawcords helping to seal in heat.

Zip Baffles & Collars

• The Gemini™ Baffle System offers a sleek, low-bulk solution that significantly cuts heat loss through the zip area.
• The Lode Lock™ System combines a magnetic closure with a mechanical lock for quick, one-handed operation.
• A built-in, adjustable, down-filled neck collar adds an extra layer of insulation when the temperature drops.

Additional Features

• A waterproof roll-top stuff sack is included, helping to save space in the pack while keeping contents dry
• A storage cube is also provided to maintain down loft when the bag is not in use, promoting longer-term performance and care.
  
  

Specifications

Technology

	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. Underpinned by the Responsible Down Standard, it is based on independent audits and a rigorous paper trail.
	Down 700 Down is the finest insulator. Manmade insulations cannot match its warmth-to-weight ratio, compressibility, long lifespan, and softness. Duck Down is great for insulated clothing and equipment for all but the most serious expeditions.
	Helium Helium fabrics are exceptionally light, compressible, and soft. Their densely woven construction ensures the highest levels of down-proofing and wind resistance.

Video