Climbing durable, trail light, midlayer or standalone, the versatile Proton's breathable thermal protection delivers comfort across a range of temperature and output levels. Octa Loft knit insulation provides warmth, resists packing out, and allows airflow to regulate comfort. Abrasion-resistant Fortius Air 20 fabric stretches, resists wind, and allows temperature-regulating airflow. A zippered chest pocket secures a radio, articulation aids mobility, and the low-profile insulated hood adds warmth.