Arc'teryx Proton Hoody (Men's)

The Proton Hoody is the active insulation layer Arc’teryx built for the full range of high-output mountain use: climbing approaches, ski touring, winter trail running, cold-weather days where you’re generating enough heat that a standard insulation piece would shut you down within minutes.

The shell is Fortius Air 20, a 84% nylon / 16% elastane face fabric that’s air-permeable rather than windproof. Excess body heat and moisture pass through rather than building up inside. The insulation is Coreloft Compact, 80gsm in the body and 60gsm in the hood, which is on the warmer side of the active insulation category. Coreloft stays functional when wet and is made from 100% recycled materials. A 20-denier Toray plain weave liner keeps airflow moving from inside as well. Fortius Air 20 is notably durable for its weight, over 60 times more abrasion-resistant than industry-standard fabrics in that denier range, which is why the Proton holds up under a harness and a pack in a way that lighter active insulation jackets don’t.

At 400g it’s not the lightest active insulation layer in the category, but it is among the most capable active layers out there. The warmth-breathability balance sits toward the warmer end, which is the right call for belays and cold dawn starts, but means you may pull it off at hard effort in milder temperatures.

Helmet-compatible insulated hood, two zippered handwarmer pockets, one zippered chest pocket. No-Slip Zip front zipper with dual back flaps to block wind. PFAS-free DWR. Articulated patterning throughout. Trim fit.