Mythic Ultra 360 Down Sleeping Bag

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UOG TOP PICK—The Rab Mythic Ultra 360 Down Sleeping Bag is a high-performance option for ultralight backpackers and alpinists. It features Thermo Ionic Lining Technology for maximum warmth and breathability. It’s impressive feature set makes this one of our top picks

Rab says: 

For mountain marathon runners and committed alpinists who need to travel light, the Mythic Ultra 360 is a game changer.

Built from lightweight recycled 10D Atmos™, it uses Thermo Ionic Lining Technology (TILT) to coat the fibres with titanium, helping reflect radiant heat back towards your body 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.

Filled in the UK with 900FP down and weighing in at just 645g, the Mythic Ultra 360 provides one of the most efficient warmth-to-weight ratios available.

Our Verdict

The Rab Mythic Ultra 360 Down Sleeping Bag is a cutting-edge option for ultralight backpackers and alpinists who demand maximum warmth with minimal weight. This innovative bag introduces Thermo Ionic Lining Technology (TILT), which reflects body heat without compromising breathability.

Temperature-wise, the Mythic Ultra 360 is impressive for its weight class. With an ISO EN comfort rating of -2°C and a limit rating of -8°C, it’s suitable for three-season use in various mountain environments. 

Weighing just 649g for the regular size, this bag offers an exceptional warmth-to-weight ratio. The 900 fill-power down and trapezoidal boxwall construction ensure optimal loft and even heat distribution.

The Rab Mythic Ultra 360 Down Sleeping Bag is not just about performance. It’s also about environmental consciousness. The 10D recycled Atmos™ shell with fluorocarbon-free DWR balances durability and weight savings. The hydrophobic down treatment is also fluorocarbon-free, reflecting the brand’s commitment to sustainability.

With its compact packed size of 36 x 18 cm, the Mythic Ultra 360 is ideal for space-conscious adventurers. While the premium materials and technology come at a higher price point, this bag represents the pinnacle of performance for those pushing the limits of lightweight backpacking and alpinism.

– Reviewed by Ultralight Outdoor Gear

Features

• Weight saving baffle construction, preventing down shift/migration
• Trapezoidal boxwall construction, to maximise loft and warmth
• Proportionally designed differential cut
• Anti snag bonded zip guard
• Ergonomically designed internal collar and hood
• Angled foot box for relaxed sleeping posture
• ½ length YKK® 3 coil main zip with noctilucent puller
• Lightweight dry bag compression stuff sack

Specifications

• Regular weighs: 649g (excluding storage bags)
• Long weighs: NA
• Sleeping Bag Length: (reg) 215cm / 84.6in, (long) 230cm / 90.6in
• Max User Height: (reg) 185cm / 72.8in, (long) 200cm / 78.7in
• Internal Shoulder Girth: (reg) 160cm / 63.0in, (long) 162cm / 63.8in
• Internal Hip Girth: (reg) 134cm / 52.8in, (long) 136cm/53.6in
• Internal Foot Girth: (reg) 102cm / 40.2in, (long) 104cm / 40.9in
• Rab Sleep Limit: -8°C (20°F)
• ISO EN: Comfort; -2°C ( 28°F), Limit; -8°C ( 18°F), Extreme; -27°C ( -17°F)
• Packed Size: 36 x 18 cm/14.2 x 7.1 inch

Material & Construction

• 10D Recycled Atmos™ (27gsm) with Fluorocarbon-Free DWR
• 10D Recycled Atmos™ (28gsm) with Thermo Ionic Lining Technology (TILT)
• 900FP European Goose Down with Nikwax Fluorocarbon-Free Hydrophobic Finish (360g/12.07oz)

Help & advice:

• The Ultimate Guide to Lightweight Sleeping Bags
• Time-Saver Guide to Choosing a Sleeping Bag
• About Rab
• Rab Mythic Sleeping Bag Range Explained
• Rab Sustainability and Responsibility
• Down Quality
• All About Down
• Hydrophobic Down
• Recycled Content in Outdoor Gear