Rab Mythic Ultra 360 Down Sleeping Bag

-8°C Comfort Limit (EN13537:2016), 360g of 900+ Fill Power Hydrophobic Down (US Method)
Weighs 624g (excluding stuff sack)
Code: SS20252V
  • From £699.99
  • (FREE UK & EU Delivery)
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The Mythic Ultra is pushing the boundaries for technological advancements in sleeping bags. The warmth to weight ratio is spectacular thanks to the use of the Thermo Ionic Lining Technology and a combination of the best and lightest materials available. This is an exciting high performance sleeping bag.  

Rab says:

With its world-first heat-reflective Thermo Ionic Lining Technology, the Mythic Ultra 360 delivers pioneering protection for those who need to make every gram count.

For mountain marathon runners and high-end alpinists who need to travel light, the Mythic Ultra 360 is a game changer. Built from ultra-lightweight 7D ripstop nylon, it uses Thermo Ionic Lining Technology (TILT) to coat the fibres with titanium, helping reflect the user’s radiant heat back into the bag without compromising the fabric’s breathability. While that reduces the amount of down required for a given level of warmth, the angles of the bag’s trapezoidal boxwall construction also improve the evenness of down distribution, eliminating cold spots.

Made in the UK with 900 fill power R.D.S. Certified European goose down, a weight of just 606g ensures the Mythic Ultra 360 provides one of the most efficient warmth-to-weight ratios in the world.

Rab's Mythic Ultra 360 Down Sleeping Bag is a superb example of what can be achieved through developing technology with this serious impressive piece of kit. The Mythic Ultra 360 uses just 360g of exceptional quality 900+ fill power down to reach an impressive Comfort Limit of -8°C. Usually this would not be enough down for that temperature rating but Rab have developed TILT, a Thermo Ionic Lining Technology which lines the inside of the bag. In simple terms this lining reflects the heat of the user back in reducing heat loss without affecting breathability.

The advanced boxwall construction uses trapezoidal baffles to allow the down to loft more effectively while eliminating the risk of cold spots. The overall weight of this bag has been kept down to just 606g with the combination of the top quality down, the special lining and using lightweight 7D fabrics. The down is able to loft quickly and effectively as soon as you get it out and give it a shake. Although it's not the roomiest of bags the fit certainly works well at reducing areas of cold air and keeping you warm through the night.

As you would expect with a bag for designed for this kind of temperature, there is an ergonomically designed collar and hood, angled footbox and anti-snag zip guard. However, as you might expect for a bag like this, it is a pretty slim fit, has a small zip making access slightly more restrictive and the fabrics used need to be treated with care to avoid damage. Overall, this is an amazing bag which is aimed at experienced backpackers and alpinists who value warmth and weight.

- Reviewed by BasecampGear

Help and advice:
  • Super lightweight 7D Ripstop Nylon Outer Fabric
  • Super lightweight 7D ripstop nylon with thermo ionic lining technology (TILT), heat reflecting to boost warmth
  • 900+FP R.D.S Certified European Goose Down
  • Rab® Flourocarbon free Hydrophobic Down developed in conjunction with Nikwax®
  • Weight saving baffle construction, preventing down shift/migration
  • Trapezoidal chamber design to eliminate cold spots
  • Proportionally designed differential cut
  • Anti snag bonded zip guard
  • Ergonomically designed internal collar and hood
  • Angled foot box
  • ½ length YKK® 3 coil main zip with noctilucent puller
  • Lightweight Dry bag compression stuff sack
  • Cotton storage sack
  • Filled in Derbyshire UK
  • Left zip only
  • Temperature tested to new European standard: EN1357:2016

Temperature Rating

  • EN13537:2016 Comfort: -2°C (28°F)
  • EN13537:2016 Comfort Limit: -8°C (18°F)
  • EN13537:2016 Extreme: -27°C (-17°F)
  • EN13537:2002 Rab Sleep Limit: Limit; -8°C ( 18°F)

Regular Specs

  • Weight: 624g (excludes storage & stuff sack)
  • Packed size:  x cm
  • Fill weight: 185g
  • Max user height: 185cm
  • O/A length: 215cm
  • Shoulder width: 70cm
  • Hip width: 52cm
  • Foot width: 41cm


  • Shell Fabric: 7D Ripstop Nylon
  • Liner Fabric: 7D ripstop nylon with thermo ionic lining technology (TILT)
  • Insulation: 900+ FP R.D.S. Certified European Goose Down

What is the 'RAB Sleep Limit'? - The recognised method of testing sleeping bags is by using the standard EN13537 temperature ratings, which are carried out by independent testing houses. The test is performed with the sleeping bag resting on an insulating mat to simulate the bag in use. The same sleeping mat is used for all testing of all sleeping bags.

RAB's view is that the sleeping mat used is inappropriate for bags designed for very low temperatures because a user would be sleeping on a highly insulative winter orientated sleeping mat, not the standard one used in the test. The test results would therefore indicate a lower performance for the sleeping bag than a user would experience in a typical situation.

RAB have therefore defined their own 'RAB Sleep Limit' as the equivalent 'Comfort limit' but based on their athletes experience and extrapolating results from other bags.

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