Peter Macfarlane feels instant warmth for the Rab Mythic 600, an excellent, lightweight winter bag.

The Rab Mythic 600 is by far the lightest bag I had in this comparative test but there are no corners cut to reach the weight. The fabric and components are very light and the quality of the down is very high.

Peter’s Best in Test 2025

The weight, pack size, comfort and performance all tie together to make the Rab Glacier 700 excellent for carrying into the winter hills for high camps as well as camp site and bothy use.
Pros
  • comfort
  • weight
  • performance
Cons
  • price
Quick specs
Price: £660
Weight: 886g
Fill: 600g of 900FP European Goose Down with Nikwax Fluorocarbon-Free Hydrophobic Finish
Shell: 10D Recycled Atmos 27gsm polyamide with Fluorocarbon-Free DWR, inner and outer
Construction: chevron pattern trapezoidal baffles, zip baffle, adjustable hood and shoulder baffle
Zip: ¾ two way
Length: 215cm
Rating: comfort: -5°C; limit: -12°C; extreme: -32°C
Sizes: one size
Women/Men’s version: unisex
rab.equipment

Happily the bag isn’t cut too close to save weight and I can sleep very comfortably with good upper body movement and easy knee bending is possible. The toe box has a shape that allows your feet to rest slightly splayed without compressing the baffles around your feet, a little detail perhaps, but it adds a little comfort.

There is a well-shaped shoulder baffle which is easy adjusted with a bungee. The hood feels a little minimalist but is well filled with down and gives good protection and is easily adjusted with a bungee which faces inwards.

The baffled lightweight main zip can snag quite easily when I’m in the bag and zipping up, but with a little patience it can run smooth.

It is extremely comfortable inside with a very soft fabric against the skin and warmth is immediate.

best cold weather sleeping bags - The Glacier offered PTC 'instant warmth' _credit Daniel Hug
The Mythic 600 offered PTC ‘instant warmth’. Credit: Daniel Hug

Loft is very good and the bag is extremely compressible for packing. I could have easily compressed it more than the 20cm x 23cm I measured in the sack I used for the review.

The DWR finish is very good with wetting out taking a long time to occur and the down inside is hydrophobic to retain performance when it does get wet.

Other features are limited to hanging loops to keep with the minimalist light weight of the nature of the bag.

The weight, pack size, comfort and performance all tie together to make the Rab Glacier 700 excellent for carrying into the winter hills for high camps as well as camp site and bothy use, but this performance does come at a price.

Testing notes

Peter used the bags at camp and in bothies from late autumn 2023 to spring 2024 over a variety of conditions and temperatures. The packed sizes were taken from putting each the same compression sack and the weights were taken on digital scales without any stuff sack. You can compare this bag with others Peter tested in our buyer’s guide to the best cold weather sleeping bags.

This review was first published in the January 2025 issue of The Great Outdoors.