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A technical, close-fitting down sleeping bag designed for efficient warmth in extreme cold conditions
Rab says:
Slim-fitting, technical down sleeping bag blending comfort, packability, and performance. Built with 650FP duck down and L.O.F.T™ baffle construction to ensure great warmth for weight, it's ideal for alpine missions in winter conditions.
Our Verdict
The Alpine -18C uses 650-fill-power duck down with an 880g fill to deliver serious insulation, weighing 1601g. This higher fill weight provides a strong warmth-to-weight ratio for winter use, with a comfort limit of around -18°C, which feels realistic when paired with an appropriate mat. It is firmly positioned for cold mountain conditions and extended sub-zero use.
The tapered mummy cut is slim fitting, focusing on heat retention by reducing internal dead space. Despite this, it remains usable for side sleepers thanks to the sidewall baffles, which keep insulation positioned around the body and maintain loft when shifting position. The L.O.F.T construction uses alternating baffle sizes to manage down distribution more effectively, helping maintain consistent warmth without unnecessary bulk. A 3/4-length two-way zip allows for controlled ventilation, letting you regulate temperature without fully opening the bag.
The Pertex Quantum outer fabric is windproof, helping protect you from exposed conditions while remaining light and packable. Overall, the construction feels well thought out, with a focus on performance and efficiency rather than added extras. This is a strong option for those prioritising thermal efficiency, low bulk and a more technical fit for colder nights in demanding conditions.
- 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
- Tapered mummy shape
- Temperature rated in accordance with ISO 23537-2:2022
Specifications
Temperature Rating
- Comfort: -10°C
- Comfort Limit: -18°C
- Extreme: -40°C
Regular
- Weight: 1601g
- Lenth: 215cm
- Width: 80cm
Long
- Weight: 1641g
- 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 (880g / 31.0oz)
- 100% Woven Polyamide Shell , Down filled sleeping bag
