275 gsm- If you're looking for a baselayer to stand up to the coldest winter days Mother Nature throws your way - and we've had customers wear Comet on expeditions in Antarctica and Alaska - then you've come to the right place. Duckworth's proprietary Comet fabric is natural-technical mash-up, combining a pure, 100% Montana-grown Merino Wool outer layer and a polyester inner layer. Why the combo? Polyester is hydrophobic, meaning it will wick sweat and moisture right off your skin and into the hydrophilic wool layer; wool chemically begins to get even warmer when introduced to water and water vapor, thus explaining why the Comet Crew will have you feeling dry and toasty even in the nastiest conditions. By the way, this loose-fitting top is soft to the touch, meaning it works perfectly as a single layer for casual food and drinks in between runs at the ski lodge. Durable, anti-odor, moisture-wicking, quick-drying, durable, and versatile: your one-stop-shop baselayer.