For those who fancy getting themselves inducted into the full alpine experience, bivvying opens up a whole host of opportunities – and if you’re a British climber reluctant to shed out for the extortionate hut fees, an incredible adventure can be found away from the dorms packed out with snoring climbers and a chance to sleep outside with little more than a baffle hood separating you from the elements.

So how does Rab’s Neutrino Endurance 400 Sleeping Bag fare when tested on a bivvy below Aiguille du Tour?

Rab’s Neutrino Endurance 400 Sleeping Bag is a lightweight sleeping bag made with alpine trips in mind, with a promise of a good night’s sleep with relative warmth and minimal pack size – minus the prospect of suffering a night carrying a bright orange survival bag and sleeping on the floor of a lift station toilet…

Rab’s description:

The Neutrino Endurance 400 is designed primarily for alpine climbers, for use on bivi ledges, light-weight mountaineering trips or general winter conditions.

The Neutrino Endurance 400 features 400g of high quality 800FP ethically sourced European Goose Down and is made in a ’mummy taper’ style, offering minimum weight and pack size, without compromising on warmth.

A combination of light-weight and water-resistant Pertex® fabrics provide excellent protection from both cold and damp weather, creating an extremely comfortable bag. Key features include a close-fitting neck baffle, anti-snag webbing tape and a trapezoidal baffle design to eliminate cold spots.

The Neutrino Endurance range of sleeping bags are temperature tested to the new European standard (EN13537:2012) and are hand-filled in Derbyshire, UK.

Price: £345.00 Weight: 890g (Regular fit) Colour: Lapis  

Warmth

First things first: the Rab Neutrino Endurance sleeping bag is pretty toasty… (this is spoken from someone who has been known to wear bed socks in the middle of summer!)

Getting into the sleeping bag at 2,700m high means the ambient temperature feels fairly nippy, but as soon as you get in, it’s a snug and cosy bag that radiates warmth. The softshell and multiple layers worn before getting into bed felt no longer necessary, so as I switched between layers, I was soon warm enough in the sleeping bag before falling asleep, which means the bag was pretty efficient at retaining my core temperature. According to Rab, the temperature limits are rated in accordance with EN13537:2012, so the temperature range is set at a comfort level a 1.5°C, the Limit at -4°C and Extreme at -21°C , with the Rab recommended limit set at -6°C . For a cool night in the mountains, I was impressed to see a temperature rating at a low level for a lightweight bag.

Let’s not forget about the all important feathers. The bag clearly states in its product labelling that it has a high fill power of 800, using ethically sourced European Goose Down, certified to the ‘Responsible Down Standard.’ The down feathers have also been treated with Nikwax during the manufacturing process in order to make the feathers hydrophobic and prevent additional water absorption, using fluorocarbon-free product. Not only is it good for the environment, as well as a key example that Rab are demonstrating responsibility for sourcing sustainable methods of production for their products - its also lots better for the longevity and overall use of the product if it’s going to have a better chance of keeping you drier.

Pack Size

The Rab Neutrino Endurance 400 packs down into a small dry bag, which easily fit at the bottom of my day pack for the walk in. It certainly took up lot less room than my old sleeping bag which was bulky and awkward to fit in a 38L bag. The bonus of carrying a down sleeping bag means it can be compressed when transporting it in its dry compression sack. It also comes with a white drawstring cotton bag for storing the sleeping bag uncompressed when you’ve got the bag at home. As it’s not a super bulky sleeping bag, the uncompressed bag easily fits into the white cotton bag and doesn’t take up much room.

Fit

First impressions: there are some possible suggestions for improvement. Trying the sleeping bag for the first time, I noticed that there was some bagginess around the shoulder area and upper torso area which felt too big if you’re on the shorter side. This meant the bag was a little too roomy for my size (I’m 5’5) and therefore there were going to be some cooler pockets in the sleeping bag. However, there was some adjustable features, including an internal collar and adjustable hood which could be pulled by the draw cord so the hood comfortably around the face without restricting airflow. The shoulder/ neck baffle can be tightened using the single drawcord and a second one further up can be adjusted to stop the draft from getting in and can be secured in place with the circular velcro pads. However, I felt the bag itself was still a bit too big for me to feel comfortable in. As a consumer (who just so happens to be female), sleeping bag fit is vitally important to minimise heat loss and I would be weary of spending money on a bag if it wasn’t made with the end user in mind.

The rest of the sleeping bag felt better fitted, and I felt I had enough room in the legs to be comfortable without feeling squashed in, which Rab attribute to their ‘Proportionally assigned differential cut.’ The shape of the sleeping bag, is a ‘mummy taper’ style, meaning it fits comfortably around the face and tapers down to the angled foot box. It certainly looks less ‘mummy’ shape and a bit more fitted then previous sleeping bags I’ve owned.

Features

Rab emphasise the zips heavily on this product, with an internal ‘YKK 3 coil zipped stash pocket’ and a ‘¾ length YKK 5 coil main zip.’ There’s also an ‘anti-snag zipper webbing tape.’ What this means - in simple terms - is that the zip on the inner seam line of the sleeping bag is easy to do up from inside and the fabric doesn’t get wedged in when you’re zipping yourself in. There’s a little pocket on the inside, which is just big enough to store an eye mask and ear plugs. The Rab Neutrino is available in either left or right hand zips, meaning the bag (in theory) could be zipped to other Neutrino Endurances if needed ( though not that practical for our bivvi…)

The sleeping bag is made of Pertex® Endurance outer fabric and Pertex Quantum® inner fabric, which means the sleeping bag feels tougher and able to withstand light moisture on the surface - be it condensation or accidental water spillage. The fabric is also made with a tougher Pertex material that is able to withstand light abrasion against the granite rocks , providing an additional peace of mind that the sleeping bag wouldn’t be easily damaged nor snag easily.

The bags lining includes a Polygiene® STAY FRESH odour control treatment which helps prolong the life of the bag in order to prevent odour building up. It’s worth bearing in mind that a warm night’s sleep in the Alps as well as additional testing in warm summer means you will sweat more. Having a treated lining was an additional peace of mind, which will ultimately keep the bag fresher if aired and stored correctly, without the need for an additional sleeping bag liner.

Weight

This is a lightweight sleeping bag, weighing in at 890g. True, if you wanted to go even lighter you could go for the Neutrino Endurance 200 at 675g (Standard fit) saving 215g, but there would be a sacrifice the comfort level of being able to cope with the colder climates (Rab’s comfort level is down to 0°C rather than -6°C. ) I know that for sleeping bags, a warmer night’s sleep is much more likely to sway me as I’d be nervous about going for something lighter but colder.

Price

Were it not for the opportunity to gear test this product, there would be little chance I’d be able to justify the hefty price tag. At a RRP of £345.00, the Rab Neutrino is an expensive investment piece, which has the number of features you’d expect that prolong the life of the product ( Pertex Neutrino shell, Polygiene lining and hydrophobic down.) However, our first experience testing the Rab Neutrino Endurance was a positive one, which was a warm, relatively comfortable night’s sleep made possible with a number of adaptable features that make it an ideal performance sleeping bag ideally suited to those committed to tackling multiple alpine trips wanting key weight savings in their kit.