Arc'teryx Cerium LT Jacket

New for this autumn, the Arc’teryx Cerium LT represents the Canadian brand’s first foray into down insulation and it’s already won a few awards. Is it worth the cash? Here’s the lowdown:

Arc’teryx Cerium LT Jacket

Arc'teryx Cerium LT
Price: £240
Weight: 261g (L)

lightweight; high warmth-to-weight; packable
expensive; colour (more subdued colours are available…); no hood


It’s hard to believe that Arc’teryx don’t have down insulation in their range, so the introduction of the Cerium LT, plus the heavier Thorium AR, comes as no real surprise. I’ve had an early sample of the Cerium LT for a few months now (yes, right through the summer) and I’ve had a good chance to evaluate whether it’ll be staying in my rucksack for the winter season too.


Arc'teryx Cerium LT insideThe main insulation is in the form of 850 fill power European goose down. Fill power  is a measurement of the amount of space one ounce of down will occupy in cubic inches in the Lorch Fill Power metre used by the International Down and Feather Laboratory.  In this case one ounce of 850 fill power goose down will loft to 850 cubic inches. In the real world this is a measure of how much the jacket (or sleeping bag) will expand after coming out of the stuffsack. The warmth of a down item comes from the volume of air trapped inside the shell by the down, so a high fill power means larger down clusters and more trapped air for a given weight of down. A garment made using 850 fill power down should be lighter, pack smaller and be warmer than the equivalent garment using 650 fill power down. But also more expensive.


Arc'teryx Cerium LT collar detailDown isn’t very good when it gets wet – this can happen due to moisture entering the jacket from the outside in the form of rain or spilled tea, or from the inside via sweat and other liquid excretions. Keeping the down and moisture apart is a part of the garment designer’s job, and Arc’teryx have adopted a couple of different approaches in their pursuit of sustained fluffiness. The shell fabric is Airetica, a 20×10 denier ripstop nylon treated with a durable water repellent (DWR) coating which helps water to bead on the surface and run off rather than soak into the down. This is used on both the outer and inner faces. It’ll keep precipitation out of the jacket, but  moisture given off by the body is a different matter, and causes particular issues in winter where the opportunity to get dry may be some time away. So – the Cerium LT features “Down Composite Mapping” which places a layer of Coreloft synthetic insulation in the areas most prone to moisture build up – areas like the underarms, collar and lower sleeves. Synthetic insulation is more tolerant of moisture than down and won’t collapse so readily.

Construction and Fit

Arc'teryx Cerium LT cuff detailThis is a stripped-down jacket, with nothing superfluous or gimmicky. The down is contained within narrow stitched-through baffles – this construction technique saves the weight of box-wall baffles though can lead to cold spots along the stitching, though this hasn’t proved to be the case so far. The reversed main zip keeps the worst of the weather out and is suitably fine-toothed as befits the minimalist styling. A cord zip pull helps when wearting gloves, and the two angled handwarmer pockets are similarly equipped. One pocket contains a cord loop which secures the basic stuffsack. I was supplied with the basic jacket version of the Cerium LT – a hooded version is available which adds 30g of weight and costs an additional £20. Nonetheless, the collar is large enough to protect the neck and fitted with a small lining patch at the front along with a little house for the zip to prevent painful beard interaction. As you’d expect, the fit is close – this helps to keep the weight down as well as aiding thermal efficiency through the elimination of dead air space. The jacket fabrics are allowed maximum contact with the body to enable them to work as intended. The close fit helps with layering, and the Cerium LT can easily be used as a midlayer, replacing a heavier and bulkier fleece. Despite the close fit a lot of thought has gone into articulation, with underarm gussets and a three part sleeve construction. There’s no indication of the bottom hem riding up when arms are raised above my head, and the simple elasticated cuffs feel secure and sealed without cutting in.

Arc'teryx Cerium LT weightNumbers and Conclusion

The minimalist construction and attention to detail has resulted in a very low weight of 261g in the stuffsack  in my size L. Given the level of insulation provided this is an impressive warmth-to-weight ratio. Packed into the supplied stuffsack the jacket forms a roughly 23 x 8 x 8cm package which is easily accomodated within a rucksack. The big issue is the price. By using the highest quality fabrics and insulation, not to mention the complex construction, the RRP of £240 is high, equating to almost £1 per gram! However, this high price isn’t unusual for Arc’teryx products, and the sheer quality of the jacket goes some way to justify it. There are down jackets available that lack some of the refinement of the Cerium LT, and for most walkers the increased bulk and weight will be a small price to pay for a lower RRP. Synthetic insulated jackets are generally cheaper still, and there is a good case for using an insulation less susceptible to moisture in Scotland. Modern synthetic insulation is getting ever closer to the performance of down, but for the maximum warmth-to-weight and minimum packsize a down jacket is hard to beat, and the Cerium LT is a superb example.
Arc’teryx promotional video:

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