Review: Arc’teryx Nuclei FL Hoody

Very lightweight, windproof and warm, the Nuclei FL makes an amazing 3-season puffy jacket for just about any activity. I’ve been testing mine for about a year now and it’s definitely found a place in my pack for those summer alpine missions and just about anywhere else I need a lightweight but warm jacket.

I’m sooo embarrassed, we wore the same outfit!

A few years ago I wrote an article about the various jackets in the Arc’teryx “Quantum” line. Basically, all the jackets that have a name relating to quantum physics (Nuclei, Proton & Atom). However, at that time the only Nuclei on the market was a heavier, AR version. That version of the jacket has been discontinued now and I’m a little sorry to see it go. It was one of my favourite coastal winter pieces. Instead of updating the Quantum article with the new Nuclei, I’ve opted to simply do a one-of review. Who knows, maybe the AR will come back.

Specs & Features:

  • Insulation: Coreloft Continuous 65 (65g/m2)
  • Fabric: Arato 10r nylon (10d)
  • Fit: Trim
  • Pockets:
    • 2 x zippered hand pockets
    • 2 x internal dump pockets
  • Hood: helmet compatible w drawstring
  • Highly packable
  • Very windproof
  • Not very breathable
Nuclei FL packed into the bag attached to one of the inside pockets with a beer can for size reference. The bag is actually pretty big which makes it really easy to get the jacket packed inside. This makes it possible to add other things to the bag as well if needed.

Materials & Construction:

Spring Skiing Puffy

Unlike its predecessors which featured Gore Windstopper and Thermium membranes in different versions, Arc’teryx opted to utilize proprietary tech in the new Nuclei FL. Called AtatoTM 10D, it’s a 10 denier ripstop nylon that’s very windproof, water resistant and not at all breathable. Great at cutting the wind and trapping heat just what an insulating mid/top layer or belay jacket needs.

The Nuclei FL Insulated with 65g Coreloft. The same type and weight of insulation used in the Proton LT and fairly similar to that used in the Atom LT. Of course, the Nuclei is a very different jacket than either the Proton (an active insulation layer) or the Atom (an insulating mid-layer). It feels much warmer, is very compressible and has a much different fit, but more on that below.


The Atato 10 denier ripstop fabric is of course quite thin and can be torn when crashing through tight trees or rubbed on sharp rock. The nice thing is that, unlike a down jacket, a small rip doesn’t impact the insulation.

Fit & Feel:

The hood allows lots of room for a helmet without pulling the collar too high.

The Nuclei FL technically has a trim fit and can be worn under a shell like the Alpha SV. However, it’s still quite puffy and has as loose of a fit as I’ve ever had on a trim-fit jacket. Not at all a bad thing as it allows the jacket to move well and not seem restrictive while feeling quite warm. The soft fabric and light insulation give the Nuclei FL an almost down-like lightness.


Pros: Light, packable, warm

Cons: The fabric isn’t overly durable so you’ll want to take care of it

Overall: An ideal summer puffy or belay jacket: it packs down to nothing, is surprisingly warm and still works fairly well in the rain.

BlackSheep was provided with a review sample but of course this did not influence us in any way.