Created to offer the breathability, durability, and mobility guides and mountain professionals demand, our warmest Proton delivers air-permeable thermal performance for high-output missions in cold conditions. 100gsm Coreloft™ insulation and the Fortius™ Air 50 outer allow airflow that helps speed vapour transport and balance thermal comfort. 60gsm Coreloft™ in the sleeves and helmet-compatible StormHood™ reduces bulk, the regular fit layers easily, and articulated patterning removes restriction.