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If you plan to brave arctic-level temperatures or high-altitude adventures, this bag delivers reliable warmth, thoughtful design, and exceptional comfort.
Sea to Summit says:
The Alpine sleeping bag features the highest quality Ultra-Dry down and a contoured mummy fit for efficient insulation. With space to cater for additional winter gear and 850+ FILL Power, this lightweight sleeping bag is best suited to extreme adventures in cold climates so you can enjoy the outdoors with confidence and peace of mind.
Our Verdict
Designed for the harshest conditions, the Sea to Summit Alpine -29°C Down Sleeping Bag combines cutting-edge materials with expedition-ready design to keep you warm in extreme environments.
Its 850+ fill power-down insulation provides outstanding loft and warmth; its comfort limit will keep you warm down to -19°C/-2°F with a lower limit rating of -28°C/19 °. The down’s water-resistant treatment ensured it maintained thermal performance despite condensation challenges. The mummy fit is generous, offering room for layering or storing small items you need to keep from freezing, while the double draft collars and full-length draft tubes worked brilliantly to trap heat.
At 1,466g, it’s remarkably light considering its impressive warmth-to-weight ratio and rugged construction. The bag compresses to a manageable 26 litres, making it packable enough for severe expeditions. Its recycled nylon shell adds a layer of durability and sustainability, and a waterproof hood and foot box further protect against moisture.
- Reviewed by Basecamp Gear
Features
- Goose Down with Ultra Dry Down treatment for improved water resistance in damp conditions.
- Premium recycled 10D Nylon's waterproof and breathable features offer added protection and prevents exposure to tent wall condensation for comfort in the outdoors.
- The Free Flow Zip System has been modified by removing the footbox zip to retain maximum warmth.
- The double draft collar and draft tube enables optimal heat retention for comfort and added warmth in Arctic, cold conditions.
- Bag Intergration: Pairs with Women's Sea to Summit bags.
- Quilt Intergration: Pairs with STS quilts
- Intergration: Sea to Summit Regular Pillow fits inside hood.
- Responsible Down Standard Cerified
- Non PFC materials
Specifications
- Weight: 1466g
- Max User Height: <185cm
- Fill Power: 850+
- Fill Weight: 1000g
- Comfort Limit: -19°C/-2°F
- Lower Limit: -28°C/-19°F
- Compressed: 26L
- Fit: Expedition Mummy Fit: Roomy cut to accommodate you and the gear that you don't want to freeze
- Modified Free Flow Zip System without footbox zip: Primary zip - full length #5 with zip-plow and two sliders.
Secondary zip - 1/3 length #5 with zip-plow and two sliders
Material & Construction
- Insulation: 850+ FILL Power, RDScertified, Goose Down with Ultra Dry Down treatment for improved water resistance in damp conditions.
- Fabric: Recycled 20-Denier Nylon shell and lining. 10-Denier Nylon waterproof-breathable hood and footbox
- Baffle Construction: Vertical chest baffles,horizontal baffles lower halfand base, box wall baffleconstruction throughout.
- Collar: Double draft collars: fitted front collar and tubular back collar.
- Hood: Generous fitted hood with two soft touch adjustments. Fits a Sea to Summit regular pillow.
- Draft Tube: Double, down-filled, draft tube along top and bottom of zippers.
