Last Updated: April 13, 2022

Arcteryx Thorium vs Cerium – Similar, But Different


Arcteryx Thorium

The Thorium AR is one of the best down jackets and/or mid-layers on the market. Made with a druable outer shell and premium down insulation, this jacket is warm, durable, and great for use as a mid-layer or outer layer in dry conditions. It's lightweight, packable, and is exceptionally well made with extra design features that make life inside it a dream.
  • Weight: 15.3 oz
  • Outer Shell: Arato 30 Nylon with DWR (Durable Water Repellent) finish
  • Insulation: 750 Down & Coreloft insulation
  • Hooded Version: Yes
  • Average Temperature Rating: -12°C
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Arcteryx Cerium

The Cerium LT is made to be extremely lightweight while still being exceptionally warm. It's protective outer-shell and Coreloft insulation make it a great outer layer during dry conditions and it's incredible down insulation and low weight make it a great mid-layer too. It's incredibly warm, durable and packs down super small to squeeze into any backpack.
  • Weight: 9.9 oz
  • Outer Shell: Arato 10 Nylon with DWR (Durable Water Repellent) finish
  • Insulation: 850 Down & Coreloft insulation
  • Hooded Version: Yes
  • Average Temperature Rating: - 8°C
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Arc’teryx is known as one of the best manufacturers of performance outdoor clothing the world over. Their focus has always been to design the highest quality garments that are the best at what they’re made for; hiking, snowboarding, and anything else you might do on a chilly mountain. Not only are their products made to be the best under tough conditions, but they also have a casual look to them, so you’ll be happy to wear them around town too.

In this review, we are going to compare two of Arc’teryx’s favorite down jackets, the Thorium AR (all round) and the Cerium LT (lightweight). Both of these are premium down jackets that are made to be a mid-layer or an outer layer in dry conditions. They are made with some of the best materials, are extremely warm, and very comfortable.

Deciding which of the two jackets is right for you is a tough task. They are pretty similar with only some rather minor but in fact key differences that might be hard to spot. Here we’ll take you into a deep dive around each jacket’s specifications and from there compare how they differ in key areas such as warmth, durability, and more.


Being one of the main insulating layers you’ll need on any alpine experience, warmth is what all down jackets are about. Oddly enough, warmth is where these two jackets differ the most, and quite sneakily at that.

The Thorium AR is insulated with 750 European goose down, and the Cerium LT is insulated with 850 fill European goose down, so which one is warmer? I’m guessing you’re going for the Cerium LT due to the higher fill down but it’s not actually the case.  And this where the specs could get the better of you.

The Thorium AR is actually the warmest and this is due to how much insulation is in the jacket. The Thorium AR weighs 15.3 oz while the Cerium LT weighs 9.9 oz and the difference is the amount of insulation. This makes the Thorium AR far warmer and better for colder use, especially as an outer layer than the Cerium LT.

The Thorium AR is rated for use down to -12°C and the Cerium LT down to -8°C. The 4°C won’t make that much difference to its everyday uses but it will come into play once you’re above the tree line in a blizzard.

Materials & Durability

Both of these jackets are very similar in regards to their materials and durability, bar the down fill we have just mentioned in the warmth section. Their quality is almost identical, both being made to the highest standards with excellent stitching and an overall exceptional build.

Both the Thorium AR and Cerium LT feature an Arato Nylon outer shell, Coreoft insulation in certain parts that repel water, and of course, their respective fills of goose down. The differences are however in the detail.

The Thorium’s outer shell uses Arato 30D nylon while the Cerium’s outer shell is made from Arato 10D Nylon. The higher D (Denier) rating equates to a thicker, stronger, and therefore more durable fabric that makes the Thorium tougher overall.

The jackets are also covered with a DWR (durable water-repellent) coating that makes them resistant to water but not fully waterproof.

If you’re likely to be using your jacket as an outer layer or generally treat your gear roughly, the Thorium is the way to go.

Arcteryx Thorium
Arcteryx Cerium


Packability is a key consideration when buying a down jacket for alpine adventures. You’ll want something that doesn’t take up valuable weight and space.

Both the Thorium AR and Cerium LT stuff down into their own inner pocket and are extremely packable, thanks to the down insulation. Down as a material compresses more than any other insulation making true down jackets ideal for slipping into your backpack unnoticed.

The fact that the Cerium LT is lighter, with a lower D nylon outer shell and less down dilling means it is the more packable of the two. It is 6.4 oz lighter and packs down much smaller.

If you’re looking for a truly light mid-layer down jacket, the Cerium LT is the better of the two in this regard.

Weather Protection

The Thorium AR and Cerium LT are made from 100% Arato Nylon and are treated with a durable water repellent coating. Nylon as a fabric has some water repellent qualities and combined with the coating, makes water bead on the surface, and fall off.

Both of the jackets are equally water-repellent but, these jackets are not waterproof, nor are they designed to be out in the rain. Down jackets are made to be insulators and once wet lose most of their insulating ability. So it’s best to just use it for what it’s made for, keeping you very warm.

In terms of wind protection, they are also pretty much identical. They’ll block the wind enough but not fully, when it’s cold and windy, it’s best to add a hardshell and let the down jacket keep you warm underneath.

Arcteryx Thorium
Arcteryx Cerium

Style and Fit

There are almost no differences between the style and fit of the Thorium AR and Cerium LT. They both come with an inner pocket, two outer hand pockets, elasticized cuffs, insulated collar, chin guard, and are hip-length with a drop-tail hem.

The quilting on the Cerium is better to look at and its shiny outer shell may be preferred by some. It also has a more streamlined design and is slim fitting while the Thorium is a tad bulkier.

Overall, they are both soft on your skin, super comfy, and cozy. The Cerium is lighter and if you want a lighter feel to your jacket over other features, it’s the right one to choose.

Value for Money

Everything Arc’teryx makes is expensive and for good reason, their quality is undeniable. Both the Thorium AR and Cerium LT down jackets are priced at over $250m, the Cerium LT being the more expensive of the two.

The reason for this is most likely the low weight and use of 850 down fill. The Cerium LT might be less warm and less durable but being ultralight in the outdoors market means a significant price increase.

Prices will differ between retailers and right now you’ll be looking to pay about on average, $50 more of the lightweight Cerium option.

They are both good value for money and the choice is yours as to whether you want to pay a bit extra for the lighter LT or a bit less for the warmer AR.

Final Thoughts

Overall Thorium AR and Cerium LT are similar in terms of materials, construction, and their primary use as a mid-layer insulating down jacket. Both are incredibly warm and very well made, and if you’re looking for a down jacket, you’re looking at the right two to choose from.

Which of the two is best for you is another question and depends entirely on what you want your jacket for and what you’ll most likely use it for most.

If you’re looking for warmth, durability, and a jacket that is better at being an outer layer, then the Thorium AR is the obvious choice. You’ll also save a few dollars too but have to live with a bulky fit.

If you’re looking for a true mid-layer that’s super light, super warm, extremely packable, and slim-fitting, then the Cerium LT is one for you.

They are both incredibly awesome down jackets and you can’t put a foot wrong by buying either of them. If you can afford it, why not but both, you won’t regret it.

Arcteryx Thorium
Arcteryx Cerium