Arc’teryx Nuclei FL Jacket Review

The Arc’teryx Nuclei FL jacket is back, but is it as good as its much-loved predecessor? Is it better?

Launched in 2015 as a mid-warmth alpine layer, the Arc’teryx Nuclei FL jacket drew a well-deserved reputation amongst climbers and hikers as a cult-classic – light and compressible enough to hang inoffensively off your harness, but cosy enough to ward off teeth-chattering during wintery belays.

In fact, legendary Canadian climber Will Stanhope all but lived in his Nuclei during three gruelling years projecting North America’s hardest alpine climb, the east face of Snowpatch Spire.  

But then, all too soon, the Nuclei was discontinued in 2017. 

Now, summoned from the grave with a spate of new specs and features, we look on and ask – was Arc’teryx right to wrench the Nuclei out of the archives and into 2020 (a year that admittedly isn’t known for getting everything right)?

I took the jacket down to NSW’s Snowy Mountains region to put it to the test.

Cosiness

First up – cosiness. In cold conditions, I normally think about being cosy, not just warm. What that means is having the right amount of insulation, as well as a layer to stop the wind from snatching that warmth away.

One of my favourite things about the Nuclei was how well it did on both fronts. Even standing at the summit of Mt Kosciuszko on a very windy day, I barely felt a gust under my jacket. This owes to the Arato 10D ripstop material lining the jacket, specially designed for enhanced windproofness and thermal efficiency. Tick.

In terms of warmth, the Nuclei is loaded up with Coreloft insulation – one of the better-performing synthetic fibres out there. Combined with the jacket’s loftiness (puff), this means there’s plenty of air captured within the jacket for the Coreloft to heat up, keeping you warm.

Although I admittedly tested the jacket in a shoulder season, I’ve read plenty of accounts of skiers and winter climbers taking this out as their go-to insulation layer. Come winter next year, it’ll be front of mind when I’m packing for backcountry skiing trips.

Weight and Packdown

Weight matters. On expeditions out, often your warmest layer only comes out for a few of the coldest parts of the day, so it doesn’t make sense to weigh your pack down with something not getting a ton of mileage. 

Again, I was really impressed with the Nuclei on this front. This owes to one of the major changes made by Arc’teryx when they gave the Nuclei the Lazarus treatment. Since 2015, they’ve moved away from a clumped-fibre Coreloft material (weighing 80 grams p/metre) and developed a layer-fibre material (achieving superior warmth at just 65 grams p/metre). Yep, lighter and warmer. 

Overall, the jacket now weighs in at 325 grams – super light for the warmth it packs.

The jacket’s puffiness means it’s also highly compressible, squashing down into an included stuff sack measuring around 20cm in length (smaller than a Nalgene bottle). Tick.

Durability

Having achieved weight-saving on the Nuclei’s insides, Arc’teryx used some of those freed-up grams to work on its outsides. That Arato 10D ripstop material I mentioned earlier was designed to be as abrasion-resistant as possible for the weight. At first touch, it feels light and potentially tearable, but I got less concerned the more I tugged and played around with it.

Other reviews I’ve seen comment on its surprising durability – one noted that after a year’s worth of use while climbing, the jacket still showed no real signs of wear or abrasion. I guess time will tell for my Nuclei, but I’m quietly confident. 

The one trade-off I’m aware of with the 10D material is breathability. There are jackets that do this better, although it invariably sacrifices windproofness. For me, I’m inclined to remove insulation layers altogether when things get strenuous and sweaty, so this doesn’t matter much to me. But some outdoors-folk prefer something you can keep on all day – just a question of preference.

Features

Unsurprisingly for a company with an in-house climbing team charged with testing and iterating their designs, the Nuclei has some handy features.

I particularly love the hood – large enough to fit around a helmet, but also adjustable enough to shrink down to noggin-hugging dimensions. This owes to the drawcord on the back of the hood, easy enough to use with a few instructions from your girlfriend/hiking partner.

The hem of the jacket is also adjustable via two draw-strings – handy for cinching in to keep wind out, or for loosening to accommodate harnesses (or any enhanced post-pandemic body mass).

There are two toasty hand pockets on the front of the jacket, as well as two large hidden pockets inside. The latter are perfect for stashing away the stuff-sack when not in use, or for snacks, maps, gloves or other bits of gear. 

Finally, with elasticated sleeve cuffs and gusseted underarms (supporting a full range of arm movement), there’s not much more I could think to pen on a jacket wish-list.

Final Thoughts

I really like this jacket. 

Needless to say, the Arc’teryx Nuclei FL is not a one-size-fits-all garment for use all year round. But for winter months or spring/autumn days up in the mountains, this is a great option for all ye appreciators of cosiness out there.

Aidan was provided with the Arc’teryx Nuclei FL to review and got to keep it. The views are entirely his own.