For a jacket that weighs just 239g on the OM scales the Arc’teryx Cerium LT is almost indecently warm. Our experience is that there’s a sort of sliding scale with down and once you get down to sub-300g levels, it starts to become a losing battle between weight and warmth, but the Cerium simply bucks that trend.

What’s Going On?

How does it manage it? As ever with Arc’eryx, it’s down to a combination of using top notch components – in this case mostly 850 fill power European goose down and ultra-fine, lightweight Airetica™—100% nylon 20×10 denier ripstop fabric.

The best way of getting that over is probably to note that somehow, although the matte finish means the material doesn’t feel remotely fragile, it’s still semi-translucent enough to be able to make out the down inside. We kind of like that.

Those baffles are sort of ‘midi-micro’ as well, presumably somewhere around the optimum size for maximum insulating efficiency.

Optimum Cut

Talking of which the cut is beautiful in that typical, tapered, close-fititng Arc’eryx way. There are no tight spots for us and no inefficient loose air-gaps either. It is pretty much perfect in pure performance terms, though obviously that’ll depend on how you’re built too.

Other stuff worth noting is that the cuffs, shoulders and collar actually use synthetic Coreloft™ 80 g/m² insulation rather than down on the basis that they’re the most likely parts to get damp if you’re layering the Cerium under a shell. A nice touch.

And predictably, in a good way, the jacket seems to have been beautifully put together and thought through. The pocket zips have little garages up top and reinforcement below, the cuffs sit nicely and the 6g stuff sacs is integrated in the sense that it sits on a loop in the lefthand pocket and can be used in situ, but can also be removed if you prefer to lose your stuff-sac instead.

Punching Above Its Weight

All that stuff is nice, but what really matters is that the Cerium LT packs down into a neat, light packing-friendly package that takes up minimal space in your pack, yet seems to pack a heavier than average punch when it comes to keeping you warm.

It is, and this is where we came in, eyebrow-raisingly warm for a jacket that weighs just a little over 200 grammes. Don’t get us wrong, it’s never going to be as snug as jackets packing twice as much down into bigger baffles, but if you’re looking for something that hits the sweet-spot between ultra-lightweight grammage and worthwhile warmth.

We’re planning on using it a lot this winter and will update with a full review in due course. If you prefer a hooded version, there’s also the CeriumLT Hoodie – same basic spec with added hood and approximately 35g or so added weight.

Full Spec

• Airetica™—100% nylon, 34 g/m². Tightly constructed, high tenacity, 20×10 denier ripstop nylon with DWR
• 850 fill European goose down
• Coreloft™ 80 g/m² insulation in damp-vulnerable area
• Insulated collar
• Chin guard
• Elastic cuffs
• Twin hand pockets with zips
• Includes integrated stuff sac
• Full front zip with corded puller