Tried and Tested: Arc’teryx Cerium SL jacket

The Cerium SL (£250) is definitely one of those ‘you have to try it to believe it’ pieces of kit. On paper, it seems impossible. How can a jacket offering 850 fill power warmth weigh just 165g – the weight of an apple?

This is the lightened and tweaked version of Arc’teryx’s women’s Cerium LT Hoody, launched last winter. For the new SL Jacket (also available in a men’s version), Arc’teryx has painstakingly removed weight by tweaking the fit, removing the hood, steamlining the zippers and using a Japanese taffeta nylon called Thisela, which so silky and light you can actually see the feathers through the fabric. I wore it under a shell, over a baselayer, and I kid you not, it was like wearing an invisible jacket, made of air, that magically offers high-powered warmth when you need it.

 You’d think that a material that has to be hand-sewn because it’s so fine would be prone to tears – but in fact, the exceptionally fine filaments used to create the Thisela fabric are tightly woven, creating a dense weave that is extremely durable for its weight, which is reassuring when I stuff it into my pack mid-tour (it compresses down to fit into the smallest of spaces).

Down has a tendency to lose its loft and warmth when it becomes wet, but this isn’t an issue with the Cerium SL, should you wish to wear it as an outerlayer. Like the jackets in the original Cerium range, it features Down Composite Mapping, a construction method that strategically places Coreloft synthetic insulation in areas where moisture may accumulate (ie. hood, shoulders and cuffs), and exceptionally lofty grey goose down in the core to provide maximum warmth.

Verdict: One of the lightest and best-performing down jackets we’ve tested – tech genius at its very best