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A maximum warmth, expedition-ready down sleeping bag designed for extreme cold conditions
Rab says:
Ultra-warm and robust down-filled sleeping bag providing reliable protection for cold conditions. Built to prioritise comfort with a wide mummy shape, roomy footbox, and sidewall baffles, it's perfect for backpacking and mountain treks.
Our Verdict
The Ascent -24C uses 650-fill-power duck down with a substantial 1080g fill to deliver very high levels of insulation, weighing 1848g. This level of fill is focused entirely on dependable warmth in extreme conditions rather than reducing weight, providing a stable warmth-to-weight ratio for winter expeditions and prolonged cold exposure. The comfort limit of around -24°C feels realistic when paired with an appropriate mat, offering strong protection in sustained sub-zero environments.
The wide mummy cut remains a defining feature, offering noticeably more space than most performance-focused bags and allowing easier movement in the bag at night. The L.O.F.T construction uses alternating baffle sizes to distribute down more efficiently, helping maintain warmth without unnecessary bulk. Sidewall baffles keep the insulation positioned around the body, reducing cold spots and maintaining loft when moving. A 3/4-length two-way zip and an additional arm zip help manage ventilation and tailor the level of insulation.
The Pertex Quantum fabric balances weight and durability, and the overall construction feels robust for a bag designed for extreme use. Features such as the insulated collar, shaped hood and internal pocket support comfort in harsher conditions. Overall, this is a well-balanced option for those prioritising maximum warmth, comfort and reliability in a serious cold-weather sleep system.
- Reviewed by Ultralight Outdoor Gear
Features
- L.O.F.T™ baffle technology reduces down migration, optimising heat retention and pack size
- Sidewall baffle construction for increased down loft and greater side sleeping comfort
- Anatomically fitted hood with drawcord adjustment to maximise comfort and heat retention
- Internal cordlocks positioned below the collar bone for greater side sleeping comfort
- YKK® zipped internal stash pocket
- 3D shaped neck collar with recycled Stratus™ insulation
- 2-way YKK® 3/4 length main zip with synthetic-filled baffle
- YKK® anti-snag zip insert and anti-snag internal zip guard
- Anatomically shaped foot box for relaxed sleeping posture
- Drawcord stuff sack included
- Zipped storage sack with water-resistant base for home storage
- Hand-filled in Derbyshire UK
- Wide mummy shape
- YKK® zipped arm access vent with integrated snap closure to retain heat during tent-based tasks
- Temperature rated in accordance with ISO 23537-2:2022
Specifications
Temperature Rating
- Comfort: -15°C
- Comfort Limit: -24°C
- Extreme: -49°C
Regular
- Weight: 1848g
- Lenth: 215cm
- Width: 80cm
Long
- Weight:N/A
- Lenth: 230cm
- Width: 80cm
Material & Construction
- 20D Pertex® Quantum nylon ripstop (38g/m²) with fluorocarbon-free DWR
- Lining: Recycled 20D nylon, 38g/m²
- 650FP European duck down with Grangers fluorocarbon-free hydrophobic finish (1080g / 38.1oz)
- 100% Woven Polyamide Shell , Down filled sleeping bag
