Rab Mythic 400 Down Sleeping Bag

-6°C Comfort Limit (EN13537:2016), 400g of 900 Fill Power Hydrophobic Down (US Method)
Weighs 688g (excluding stuff sack)
Code: SS18182
  • £359.99
  • (FREE Delivery on orders over £15)
  • RRP £459.99
Item out of Stock | Usually dispatched within 24 hours

The Mythic 400 is a super-lightweight sleeping bag filled with high quality Rab Fluorocarbon free Hydrophobic, 900 fill European goose down and uses very light Pertex Quantum GL fabrics.

The Mythics are now the best performing range of sleeping bags that Rab produce in terms of warmth-to-weight.

The trapezoidal chevron baffle system is used to provide very efficient warmth and the best possible use for the 900 fill hydrophobic goose down that is used. The superlight Pertex Quantum GL fabric allows the down to hug the body providing maximum levels of warmth and minimum ‘dead-space’ in the bag.

The Mythic 400 is an ideal companion for anyone who wants maximum warmth for minimum weight whether for lightweight backpacking and adventure racing mountain marathons.

Rab says:

The pinnacle of innovation, the Mythic 400 Sleeping bag is an ultra lightweight down sleeping bag with the best warmth to weight ratio in the Rab range. Designed for mountain activists looking to reduce weight while moving through the mountains, for use in cold environments where weight and packsize are crucial to success such as long summer alpine routes, and multi day trekking.

Since our beginnings when Rab Carrington hand stitched the first sleeping bag to bear his name, Rab design has drawn on experience from years spent in the mountains. The Mythic Sleeping Bag continues that tradition, once again pushing the boundaries in innovation and design.

Weighing in at 660g the Mythic contains 400g of the highest quality 900 fill power ethically sourced European goose down. Achieving an exceptional warmth to weight ratio, this bag retains all the features you need to stay warm and protected in cold mountain environments. The tapered mummy shape with angled foot box gives a generous fit for the weight. Weight saving baffle construction prevents down shift, while the chambers are angled downwards in chevrons keeping the down over the centre of the body to ensure core warmth throughout the night. Each bag is hand filled in Derbyshire using Hydrophobic down developed in conjunction with Nikwax®.

The internal collar is ergonomically designed, and collar, hood, and internal baffles have drawcords which can be cinched in for extra warmth. Featuring a half length YKK main zip with glow in the dark puller, while the bonded zip guard works as a draught excluder. Super lightweight trims and features reduce weight, and the dry bag compression stuffsack ensures protection from the elements and a smaller packsize while on the move.

Every element of the Mythic 400 is designed to deliver optimum warmth for minimum weight, allowing you to withstand the challenges of moving fast and light in alpine environments.

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I've used the Rab's Mythic for quite a few nights and it definitely lives up to its rating, I tend to sleep cold but had no problems keeping warm without any other clothing, on a decent sleeping mat.

Reducing the weight of the sleeping bag ‘shell’ is exactly what RAB have done with the Mythic sleeping bag range, and they’ve managed to do it with very little compromise on features. I’m very glad they didn’t give in to the temptation of a ‘sewn through’ construction which can cause cold spots.

The zip is interesting – it comes apart at the bottom, I’m pretty sure this is aimed at multi-day climbers but I undid the zip to attend to a call of nature and the parts separated at the bottom, it was a frustrating struggle to get them together and zipped up again.

I liked the cordlocks on the hood and shoulder baffle, these are easy to use, there is an anti-snag baffle along the main zip which worked about as well as on other bags. Space-wise I found it perfectly adequate. There aren’t many bags around achieving such good results at such low weight, and some that do compromise more on features than the Mythic bags.

- Reviewed by Ultralight Outdoor Gear

Help and advice: Choosing a sleeping bag advice EN 13537 rating for sleeping bags explained All about down filling in sleeping bags
Sleeping bag shape and sizes advice Sleeping Bag features Page 1 Sleepin bag features page 2
| RAB Premier Sleeping Bag Stockist - Ultralight Outdoor Gear is a RAB Premier Sleeping Bag stockist. RAB recognises our knowledge and experience when it comes to advising customers about the sleeping bag that would best meet their needs. It also recognises the comprehensive range of RAB sleeping bags that we stock.
Read reviews here:

Read reviews here:

  • Pertex® Quantum 7 Denier Inner and Outer
  • 900 FP R.D.S Certified European Goose Down
  • Rab® Fluorocarbon free Hydrophobic Down developed in conjunction with Nikwax®
  • Weight saving baffle construction, preventing down shift/migration
  • Trapezoidal baffle chamber design
  • Mummy Taper Shape
  • Proportionally assigned differential cut
  • ½ length YKK 3 coil main zip with noctilucent puller
  • Anti snag bonded zip guard
  • Ergonomically designed internal collar
  • Internal collar and hood drawcord
  • Super light-weight trims and features
  • Angled foot box
  • Cotton storage sack
  • Temperature tested to new European standard EN13537:2016
  • Available in left zip only

Temp ratings

  • EN13537:2016 Comfort: -1°C
  • EN13537:2016 Comfort Limit: -6°C
  • EN13537:2016 Extreme: -24°C
  • EN13537:2016 Rab Sleep Limit: -7°C


  • Weight: 688g (excludes stuff sack)
  • Stuff sack weighs: 38g
  • Packed size: 18 x 43cm
  • Max User Height: 185cm/72.8in
  • Shoulder Width: 70cm/27.5in
  • Hip Width: 52cm/20.5in
  • Foot Width: 41cm/16.0in
  • Fabric Outer & inner: Pertex® Quantum 7 Denier Inner and Outer
  • Insulation: 900 FP R.D.S Certified European Goose Down, Rab® Fluorocarbon free Hydrophobic Down developed in conjunction with Nikwax®
Showing our 2 Rab Mythic 400 Down Sleeping Bag reviews with an average rating of Excellent. Would you like to write a review?
Review Summary - 5 out of 5 based on 2 ratings.
March 27, 2021 | Sam Knight
Super light and comfy

This bag is super light but still comfy. Has full hood, half zip with a good draft baffle, neck baffle works well. 900 fp down really does loft well. Handles damp over several nights really well compared to my non hydrophobic sleeping bags. The bag is wide enough for me to wear several layers and even a light insulation jacket when the temp really drops. I'm 6ft and 15 st. Only down side is the high price. But 900 fp down ain't cheap. Also I feel the stuff sack is a little small and was worried about over compressing it so I bought an after market all nylon dry bag, one slightly bigger and find it much easier to pack. You need to be careful with the light fabric, this is a specialist piece of kit and you need to be aware that it won't be as tough and durable as some of the heavier fabric bags. All in all, a great piece of kit if you are really serious about saving pack weight but still keeping warm at night.

Ultralight Outdoor Gear Limited
March 27, 2018 | Jack
Sleeping bag

This is a great, lightweight bag and is waterproof*
*Note from UOG - This sleeping bag is definitely NOT waterproof, although it does use hydrophobic down

Ultralight Outdoor Gear Limited