Walking Equipment and Accessories

Rab Neutrino -6 Sleeping Bag | Review

Our verdict on the -6 offering in Rab's newly updated Neutrino range. If you want something that's warm but still light, you're in the right place.

I used to work as a sales assistant in a specialist outdoor gear store, around 15 years ago now, and I distinctly remember one of the big purchases I made using my staff discount being one of the earlier iterations of Rab’s Neutrino sleeping bag. Since then, that bag has accompanied me on all manner of trips, from winter camps in the Peak District to sub-zero treks in Swedish Lapland, and I still use it. In fact, it remains a go-to when I want proper cold weather comfort.

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It cost me about £350 at the time, which felt like a huge investment, but it has more than paid for itself over the years. Now, for 2026, the Neutrino has been revamped, with three new models: 0C, -6C and -12C. I’ve been testing the -6C version. Here’s how I’ve got on with it.

How I Tested It

I used this extensively on the fringes of winter while checking routes for a guidebook. Notable trips included a very windy camp above Ullswater in temperatures around 2C, and a frosty night in the Arenig Mountains of Wales, where temperatures dropped to around -2C and I ended up sleeping on the cold ground after discovering my mat had a puncture. I also used it on a hike of the Golden Valley Pilgrim’s Trail, using it for warmth on cold, hard church floors during our early spring adventure.

On our tester’s campout in the Yorkshire Dales.

Rab Neutrino Down -6 Sleeping Bag

This is a very well-made three-season sleeping bag, with materials that feel high quality throughout. It delivers an excellent warmth-to-weight ratio and packs down impressively small, making it well suited to fast and light trips from spring through to autumn.

Will it Keep You Warm?

Rab rates this bag with a comfort temperature of 0C, a limit of -6C and an extreme of -24C. I can’t comment on the extreme rating, but I can say that I was warm enough at -2C, even without a sleeping mat, which says a lot about its insulation.

That said, it is important to be clear about where this bag sits. In real UK use, this is a three-season sleeping bag with the ability to handle light frost, rather than a true winter option. If you are regularly camping in well below freezing conditions, the -12C version would be the better choice.

Weight and Packability

At 870g, this sits at the lighter end of the three-season category. In its waterproof stuff sack, which offers excellent compressibility, it packs down to roughly the size of a small loaf of bread. It is one of the more compact sleeping bags I have used in this warmth bracket.

OM editor Will using it in early spring, going from church to church on a pilgrim trail.

The efficiency comes down to a few factors. It uses around 600g of 800 fill power European goose down, and Rab fills the bags in the UK. The baffle construction also plays a big role. Rab’s L.O.F.T 3D design uses offset seams and a helix shape to keep the down evenly distributed, reducing the risk of cold spots. In use, that translates to consistent warmth across the bag.

Is the Rab Neutrino Water Resistant?

Rab has worked with Grangers to apply a hydrophobic treatment to the down. From my experience, both with this bag and others, this does make a difference. On one trip I had damp tent walls, a damp floor and a very damp border terrier, and subsequently the sleeping bag got damp, but it retained its loft.

There are limits to any hydrophobic down, though. If you expect persistently wet conditions, a synthetic bag is still the safer option.

The Pertex Quantum outer fabric helps here too. It offers decent water resistance, good durability for the weight, and keeps out draughts while allowing the down to loft properly.

The Sizing

I am 177cm tall and found the Regular length, rated up to 185cm, to be spot on. There is enough room at the footbox to avoid compressing the insulation, but not so much excess space that you are heating empty air. A Long version is available for those taller than 185cm.

Pictured during Will’s sub zero camp in the Arenigs.

In terms of width, this is a performance fit. With a shoulder girth of 160cm, it sits close to the body, which helps with thermal efficiency. If you sleep fairly still, this works well.

If you tend to move around or sleep on your side, Rab offers a Wide version, increasing the shoulder girth to 180cm. That gives you more room and makes layering easier, but you lose a little efficiency.

Other Details

A two-way zip allows you to vent from the foot end, which is useful in milder conditions. The YKK anti-snag zip works as intended and is something I’ve definitely appreciated when getting in and out of the bag in the dark. It’s an excellent design.

The glow-in-the-dark zip pull is a small but genuinely useful touch too. Other features include hanging loops, internal cord locks, draught baffles and a small pocket near the shoulder for a head torch.

Verdict

This is a strong option for anyone looking to travel fast and light. It suits backpackers, fastpackers and bikepackers who want a single bag that covers most UK conditions outside of deep winter.

With an RRP of £370 to £490, the Rab Neutrino -6 isn’t a cheap sleeping bag, but the performance justifies the price. Like the Neutrino I bought 15 years ago, it is the kind of piece of kit that earns its keep over time.

If you want one sleeping bag to cover the majority of UK mountain use from spring through to autumn, with enough warmth to handle colder nights, this is hard to beat.

It hits a sweet spot that many bags miss: light enough for efficient travel, but comfortable and reliable when conditions turn.

A final note on Rab’s Material Facts section. This gives a full breakdown of materials, recycled content and chemical use. In this case, a large proportion of the fabrics are fully recycled, and no PFAS chemicals are used.

Pros: Excellent warmth-to-weight ratio, highly packable, high-quality materials, effective anti-snag zip, waterproof stuff sack.
Cons: Close fit may not suit everyone.

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