As most of you know, I've been sharing helpful guides to all Arc'teryx jackets for years now (full post list is at the bottom).
Recently I'm getting asked about Nuclei FL vs Proton LT a lot, so here we go.
After taking it down years ago, Arc'teryx finally decided to bring the once-loved Nuclei FL back to life in February 2020.
The overall design roughly remains the same. Outer fabric is updated to be lighter (from Arato 20 to 10), and the hood is now helmet compatible - pleasing news for climber folks.
The rest remains the same.
Now let's take a brief look at how it compares to the Proton LT.
- Nuclei FL is much more wind resistant and a little bit warmer. Unlike Proton LT, it's also packed into its own stuff sack
- Proton LT is much more breathable and a little bit more durable
If you're looking for a summary, skip to the Conclusion & Best uses heading.
Now let's get to their bolts and nuts.
Let's see where these two stand in terms of temperature ratings:
°F / °C
Arc'teryx LEAF Cold WX Parka SVX (Men's)
Arc'teryx Ceres SV (Men's)
Arc'teryx Dually Belay Parka (Men's)
Arc'teryx Thorsen Parka (Men's)
Arc'teryx Centrale (Women's)
Arc'teryx Piedmont [NEW] (Men's)
Arc'teryx Therme Parka (Men's)
Arc'teryx Camosun Parka (Men's)
Arc'teryx Radsten Parka [NEW] (Men's)
Arc'teryx Macai (Men's)
Arc'teryx Andessa (Women's)
Arc'teryx Patera Parka (Women's)
Arc'teryx Alpha IS (Men's)
Arc'teryx Radsten Insulated [NEW] (Men's)
Arc'teryx Kappa (Men's)
Arc'teryx Sensa Parka [NEW] (Women's)
Arc'teryx Magnus Coat (Men's)
Read more about this chart here in my Insulated Outerwear Temperature Ratings Guide.
These are only approximate values assuming:
- you only have a shirt under and no shell over,
- during daily use (strolls, power walks etc at most - no high output activities),
- with enough wind to cause an umbrella to twist in your hand,
- and when it's dry out.
If you think you run warmer or colder than the average person, then shift temperature ranges accordingly.
Also check out my Arc'teryx Favorites.
As you see, the Nuclei FL is warmer, but if you take wind off the table, then I'm pretty sure that the Proton LT would feel just as warm as the Nuclei FL.
Proton LT is ahead of the Nuclei FL in this department. The reason for this is actually the sacrifice the Nuclei FL makes with its incredible wind resistance performance.
Which brings me to my next point...
Almost the entire design intention of Nuclei FL is centered around one thing: Wind resistance.
Unlike most other jackets and hoodies (including the Proton LT), it lacks the baffled seams - which, typically, let the wind right into the jacket through the vacant spots.
If you live and/or perform a high output activity out at brutally windy weather conditions, this could make an incredible advantage for you.
In terms of water resistance, on the other hand, they're comparable. Considering the fact that the Proton LT is meant to be a mid-layer more than a shell, you might expect it to perform worse than the Nuclei FL in this department.
But that's not the case. They're about the same.
So where do they stand?
Well, neither are equipped with Goretex. They certainly won't be as waterproof as some solid Goretex Arc'teryx shells, but still fairly water resistant. Their DWR coating work fine as well.
DWR is a coating.
It's basically sprayed on to the surface of these jackets as a finish. It stands for Durable Water Repellent - which means that water will be repelled under wet conditions instead of soaking into the fabric.
DWR also decreases dry time.
It's a good thing these jackets are coated in DWR, but pay attention to the fact that DWR is a coating - meaning that it will wear off over time.
Which is why you might want to invest in a DWR spray such as this one for after treatment.
As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
If waterproofing is a must-have for your situation, I'd recommend you to take a look at Beta LT.
Conclusion & Best uses
- The Proton LT is designed as a breathable, insulated mid-layer for high output activities out in chilly weather. Think mountaineering, ski touring, fat biking...
Its primary points are durability and breathability. This is why I picked it as my top synthetic insulated jacket.
Additionally, it does offer some weather protection, but is best paired with a waterproof shell on top in wet weather. Otherwise it risks soaking the droplets into the fabric, especially as the DWR wears off.
- The strongest point of the Nuclei FL, on the other hand, is wind-proofing.
Under windy conditions, this also makes it a warmer alternative to Proton LT. As you see, it works as a more complete stand-alone piece compared to the Proton LT.
Additionally, unlike the Proton LT, it is packable.
There's one thing you might wish having: Breathability.