Arc'teryx Nuclei FL Review

Arc'teryx has been cranking out high-quality insulated puffys for decades, but the Nuclei FL is the first one we've encountered that perfectly fits the needs of the summertime alpine climber or any climber who is up high, belaying as the shadows start to fall. The Nuclei is similar to several past award winners and has many of the same features, but it functions better than its competition, making it our favorite insulated jacket for climbing or as a midweight layer for hiking and camping.

This model manages to add more insulation, puff if you will, without making it heavier than its closest competitors. In terms of warmth-to-weight ratio, it's a masterpiece that has everything we look for in an “on route” puffy — without the fluff. It stuffs into a small included stuff sack, not its own pocket, and even this simple feature is an improvement on traditional designs.

Performance Comparison

Warmth

The Nuclei's 65 grams of Coreloft seems to be the sweet spot for keeping the weight low while providing plenty of insulation. Unlike some other popular insulated jackets from Arcteryx, the Nuclei doesn't have any stretchy panels for venting or increased range of motion, just uniform insulation under the arms, across the shoulders and back, and everywhere else, including the hood. Other warmth-inducing features include cinch cords at the hem and on the back of the hood, and elastic on the wrists.

We found this puff more than adequate when placed over a midlayer on days at the crag where temps never climbed past the low fifties in the shade. On route, it's perfect to pull out as soon as you reach a belay to seal in all the heat you built up while climbing. We also pulled this jacket out on windy summits and ridges during some spring ski touring. It kept the wind at bay while we took photos and waited for our splitboarding friends during transitions.

Weight and Compressibility

On our scale, the men's small Nuclei weighs in at 10.5 ounces.

It's not the lightest insulated jacket in our review, but it's within two ounces of the lightest and still provides plenty of warmth. Unlike the Arc'teryx Atom LT or the Proton, the Nuclei includes a stuff sack.

This stuff sack is permanently fixed to the inside of the jacket and sits conveniently inside the right side drop-in pocket. This stuff sack is roomier than most of the pockets on competing models stuff pockets, making putting the Nuclei away or taking it out at belays much easier. We found it very easy to clip the stuff sack to the anchor and pull the jacket out without any fear of dropping it, and could easily reverse the process to stow it away. You won't get pumped stuffing this jacket away, and you're less likely to drop it while pulling it out, so you won't hesitate to put it on, even if you're just a little cold. The result is that you'll stay more comfortable on route, looser, more relaxed, and primed to send when you leave the belay.

Comfort

Though not as comfy as a soft, breathable jacket, the Nuclei feels nice against the skin, and its Arato 10D ripstop shell fabric doesn't feel like a crinkly garbage bag. In the past, a few of our testers have lamented that Arc'teryx jackets fit a bit short at the hem. The Nuclei felt about perfect under or over a climbing harness, and it tapers down in the back for extra bum warmth.

A size small fit our 5'9" 150 pound lead tester perfectly. It doesn't restrict movement and is still large enough to fit over a fleece and lightweight jacket. The hood features a drawstring to keep it in place over your bare noggin, and it's large enough to fit over a climbing helmet.

Two zippered handwarmer pockets are ample enough for a few bars, a topo, and a headlamp, and there are two internal drop-in pockets to keep gloves or even climbing shoes warm. This jacket doesn't have a chest pocket, but we can't say we really missed it all that much. If there is one thing we'd add, it'd be a two-way zipper to help keep the jacket out of the way of our belay loop.

Weather Resistance

The Nuclei keeps the wind out with Arc'teryx's proprietary Arato shell fabric.

This ten denier ripstop nylon isn't completely waterproof, but it does an admirable job at keeping us dry in snow and light drizzle and even did well in a simulated downpour. After two months of testing, the DWR coating is holding strong and still causing water to bead off the jacket instead of wetting out the shell fabric.

Breathability

This compact puff keeps your body heat close and keeps the weather out, allowing little permeability for breathing.

Moving quickly on approaches, we could barely go a mile without needing to stop and take it off before getting uncomfortably sweaty, but that's how you know it's working! At least the synthetic Coreloft insulation won't lose its loft if you happen to saturate it with your perspiration. In all seriousness, athletes on the move will need a more breathable layer if they want a jacket they can leave on, while the Nuclei keeps you warm once you've stopped moving.

Value

This jacket is priced similarly to the best Patagonia models and its quality and refined design are on par with other excellent products we've tested from Arc'teryx. If the price is too steep, it's worth checking out other models, like the Rab Xenon, which is very close to matching the Nuclei in performance but retails for nearly half the price.

Conclusion

The competition is stiff, but the Arc'teryx Nuclei ekes out a win. You can't go wrong bringing this model with you for multi-pitch climbing, spring ski touring, camping, or even as a warm layer to throw on before you run errands around town. In terms of a puffy to bring for climbing long routes, the Nuclei is as near to perfection as we've seen.