Rab Mythic Ultra vs. Neutrino: -6°C sleeping bags
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If you are looking for Rab Mythic Ultra vs Neutrino, it is best to establish the generation first. This comparison pits the Mythic −6 °C QSN-25, which also appears commercially as Mythic Ultra, against the Neutrino −6 °C QSN-16. It does not compare the older Mythic Ultra 180/360 models with the older Neutrino models numbered by down weight.
Our answer: Mythic if saving weight is a specific priority; Neutrino if you prefer a versatile solution with a longer zipper. Both declare 0 °C comfort and −6 °C limit ratings. Therefore, the price or fill power does not justify claiming that one is suitable for sleeping at a lower temperature.
Comparison of current sleeping bags, Regular size
| Data | Mythic −6 °C | Neutrino −6 °C |
|---|---|---|
| Code | QSN-25 | QSN-16 |
| Weight | 700 g | 870 g |
| Down | 355 g, 900FP | 400 g, 800FP |
| Comfort / limit | 0 °C / −6 °C | 0 °C / −6 °C |
| Main zipper | ½ length | ¾ length |
| Inner shoulder girth | 160 cm | 160 cm |
| Inner hip girth | 134 cm | 134 cm |
| Inner foot girth | 102 cm | 102 cm |
| Construction | 3D L.O.F.T and TILT lining | 3D L.O.F.T |
The Mythic saves 170 g, approximately 20 %, compared to the Regular Neutrino. Their reference inner girths are the same in the master file: it would not be accurate to describe the Neutrino as more spacious in this specific comparison.
What changes when sleeping and packing
The longer zipper on the Neutrino can be practical for getting in, getting out, or venting the bag. The decision does not boil down to weight alone: think about how you sleep and how much you adjust ventilation during the night. With the Mythic, the weight savings must justify the difference in access for you.
Both use 3D L.O.F.T construction. The Mythic adds a TILT lining and higher fill power down to seek efficiency with less filling. We do not convert that technology into additional degrees: the declared thermal rating remains the same for these two models.
When to choose Mythic
We would choose it for someone who has already defined their sleep system and wants to reduce weight, especially when carrying gear for many hours. Before investing in saving 170 g, check if your sleeping pad, moisture protection, and bag fit already meet the needs of your route.
When to choose Neutrino
We would choose it if you are looking for a bag for varied outings and prefer the three-quarter zipper. If saving every gram does not determine your purchase, it may be a choice better proportioned to your use. Check availability and size on the product page: Regular, Long, and Wide variants should not be compared as if they weighed the same.
Does −6 °C mean sleeping comfortably at −6 °C?
No: −6 °C is the declared limit; comfort is 0 °C. To plan a trip, use the comfort temperature as a starting reference, consider your cold sensitivity, and leave a margin for forecast changes. The extreme temperature is not a temperature for use during a normal night.
The sleeping pad and humidity are part of the system. It is not wise to compensate for an insufficient pad by choosing a bag based solely on the number in its name.
Mountain Group Conclusion
Decide between lower weight and a longer zipper with more weight. You do not need to buy the Mythic to obtain a lower thermal limit: in the models compared, there is no such difference.
See Mythic / Mythic Ultra −6 °C · See Neutrino −6 °C
To continue choosing
Sources and compared versions
Data reviewed on September 22, 2026. Weights, fill, girths, and zippers checked against the official Elastic SS26 master file, Regular size and left zipper. Construction checked against the Rab AW26 Equipment catalog. Rab's current designation is Mythic.
Main photo: Rab / Lena Drapella. Bivouac scene with a sleeping bag from the Neutrino family; it does not represent the Mythic nor does it identify the thermal range on its own.
