The Canadian design demons of Arc'Teryx call the Sidewinder SV their "ultimate big mountain riding jacket," and are determined to keep their customers up - and their products' weight down. Thus we present to you this season's must-have "descending" jacket, the Sidewinder SV. We say "descending," because Arc'Teryx outdoor garments are separated into two categories; one for ascending (climbing) and one for descending (skiing and riding). The main differences seem to be minor - we'd be happy to wear their jackets no matter which direction we're heading.

Our citrus (yellow) Sidewinder SV jacket arrived at the MountainZone offices just in time for a huge new year's dump at California's Mammoth Mountain. We enjoyed 32-degree fresh tracks off of Cornice by morning - and freezing winds after our apres drinks each evening. A base layer and porous wool sweater was all we needed to keep warm and comfortable under the SV.

They call this "the most refined 3-ply shell in the business," and we're not about to argue. Using this season's popular Gore-Tex XCR technology married to 420 NR (lightweight) and 540 NR (tough) nylon fabric, they achieved a great mix of light weight and amazing wind- and water-proof characteristics. Gore-Tex XCR comes closer than ever to achieving the holy grail of "hardshell" fabrics - to be bombproof and breathable at the same time.

Features on the jacket begin with our favorite - a clear laminated radio pocket on the left sleeve. That same laminating process extends to this season's chic YKK WaterTight P.U. zippers (no storm flaps needed) and powder skirt - as well as the large pit zips. By keeping tolerances to a minimum and laminated/welding as many seams as possible, they've kept the Sidewinder as light as possible (just 23 ounces for the men's model!).

The SV comes with a comfy one-hand-adjustable hood, while its brother model the TR is hood-less. We like hoods, but we also like our helmets, and hope to see a bigger hood (like that found on their mountaineering jackets) in future versions of the Sidewinder. Other items on a wish list include belt loops off the powder skirt, slightly larger inside chest pockets and a bit taller collar. And finally, one of our reviewers commented that those fine storm zippers can be difficult to work with one hand. But these are small issues on an otherwise outstanding and attractive jacket.

Arc'Teryx was recently acquired by the Adidas-Salomon Group, who will add some marketing muscle to the company - but likely leave their design teams alone. This is good news because from what we've seen, these folks don't need much help making top-notch apparel - evidenced by their products' lifetime warranty.

msrp: $440
www.arcteryx.com // 800-985-6681

Special thanks to Mammoth Mountain for hosting the MountainZone testing team for this review. Contact them at 800-MAMMOTH or www.mammoth-mtn.com for your next Sierra visit.

— Reviewed & Written by Ari Cheren, MountainZone.com Gear & News Editor