Arcteryx Nuclei AR Jacket



One of the best all round  mid weight synthetic belay jackets currently available.



Both Dave and myself have the Nuclei FL jacket and Dave has reviewed it previously here. With news of the ‘AR’ version I was envisaging an ‘update’ style of review highlighting a few differences here and there. When the Nuclei AR arrived it became clear that wasn’t really an option – this is a very different jacket. The Nuclei AR is very much a full on belay jacket suitable for alpine and Scottish winter conditions.


The Nuclei AR differs from the FL in a number of ways. Materials wise a heavier 100g/m2 Coreloft insulation versus the 80g/m2 on the FL, a heavier duty seam sealed outer in N20mr-x WINDSTOPPER® (this has been supplemented for 2016/17 with N20mr GORE® THERMIUM™ as well). These changes make the jacket warmer but more importantly far more weatherproof. The shell is now pretty much waterproof – you can ‘happily’ stand on a wet belay getting dripped on as your partner inches upward and the ice melts without fear of your jacket becoming a sodden lump. Perhaps the most notable difference beyond the fabrics is the change to a full on storm hood with a laminated visor. Now the FL’s hood worked but it wasn’t the sort of ‘snuggle inside’ comfort hood that the AR possesses. The AR’s hood lets you properly seal out the elements whether you are on a belay or dossing down for the night at a bivi. Another useful addition for the winter mixed/ice climber is the drop in mesh pocket for gloves letting you warm, perhaps even dry a little, you lead gloves between pitches. Otherwise the excellent articulated sleeve cut and usual Arcteryx tailoring remain. Two minor details worth mentioning which are more areas of personal preference. Firstly the cuffs are elasticated which I like as it is one less thing to faff with and secondly the zipper is not double ended. At one time I was a big fan of double ended zippers on belay jackets but I’ve become a bit more ambiguous about them recently, suffice to say that neither of these elements impinged on the usability of the Nuclei AR in use. In terms of fit I must confess that the Medium supplied was a bit large for my petite frame (I take a small normally in Arcteryx kit) however Dave is a medium and it has now found a home on his more ‘muscular’ form 😉

In Use

The first outing for he Nuclei AR was at the tail end of the Scottish winter season – not too cold but with typical ‘dampness’ making things feel chilly and get wet. For general purpose use in Scotland it is hard to beat synthetic fill such as the Coreloft found in the Nuclei AR, it is just so much better at resisting the effects of the wet and damp, not even the various hydrophobic down mixes come close. There is no need to ‘baby’ the jacket it can go on over a wet shell and be stuffed unceremoniously into a sac whilst the spindrift is flying. The WINDSTOPPER® outer keeps the mizzle and drizzle at bay and you remain toasty warm in your little cocoon.

Waiting to start Tower Ridge

The inner mesh pocket works brilliantly for stashing leading gloves whilst you belay and I did try to stash my belay gloves there but it just seemed a little insecure when pulling the jacket out of the sac so just zipped them into the hand-warmer pockets when stashing the jacket. If need be you could comfortably walk down in the rain wearing the Nuclei AR as it’s that weather resistant but you’d probably overheat in anything but the most bitter of conditions. Packability wise it is not as compact as its lighter sibling the Nuclei FL and it tends to ‘balloon’ a bit as you stuff it in the sac, I’m guessing this is because the air can only escape via the lining with the outer shell being that much more impermeable, but there is not a lot in it to be honest. A lightweight stuff sac is supplied with an included clip in loop that works well but is probably more suited to open icefall style climbing – if you’re going to clip it to your harness and indulge in any alpine or Scottish thrutchy mixed activity then a more substantial stuff sac will be in order.

Nuclei AR (M 465g) on left Nuclei FL (S 285g) on right

Whereas I’d never consider the Nuclei FL for proper belay duty in Scottish winter (it’s not warm or weatherproof enough) the Nuclei AR happily fulfils that role.

With the winter season over the Nuclei AR didn’t see much use till the CGR summer alpine jaunt. We usually try and include at least one planned bivi and for the last couple of years I’ve used a Pied d’elephant and belay jacket combo together with an ultralight (Rab Survival Zone lite) bivi bag. This year I swapped out the usual down (it’s not Scotland!) belay jacket and used the Nuclei AR. The Nuclei AR is slightly heavier and less compact than my usual down jacket and probably slightly less warm.

Lovely evening for a bivi

However there is not a huge amount of difference and my overnight kit all still fitted comfortably into a 26 litre sac for a night amongst the rocks behind the Albert Premiere hut. To be honest it wasn’t a cold bivi and I stayed toasty in the jacket but there was no sense of clamminess so it seems to be suitably breathable for bivi duty which can be a worry with some of the more ‘weatherproof’ jackets. Come morning and the Nuclei AR still kept me toasty warm whilst brewing up and preparing breakfast and was then quickly stashed into the sac as we headed off for the day’s fun and games.


The Nuclei AR is well suited to the vast majority of alpine and Scottish winter activities. It is warm enough for most scenarios and compact enough that you won’t hesitate to bring it along. The beefed up shell not only provides improved weather resistance (and perhaps a bit of additional warmth) but promises greater durability should you ever need to climb fully togged up after you partner has spent two hours on their lead and you’ve metamorphosed into a popsicle! The only downside is the price tag but if you can afford it this will be money well spent.

RRP £400


RiCGR_RichMugchie is the enthusiastic amateur of the team. Enjoying all aspects of climbing but especially alpine, winter and his local grit . Having managed to survive the vagaries of both fluorescent Koflachs and rainbow tights in the 80s he looks forward to an even more stylish future. A shady past in mountain marathons and adventure races, including the Marathon des Sables, means he’s an advocate of fast and light. Though the former is debatable if you’ve seen him on a tricky lead!

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