For added warmth as we hit high elevation, we insulate with the Xenair Vest. Because of Pertex Quantum Air's windproof yet air-permeable design, this midlayer is great for activities where we'll be stopping plenty on our way to the top. Dual-density Primaloft insulation is body-mapped and engineered to keep our core warm while we're belaying, resting, or enjoying a trailside snack, and it's lightweight and breathable enough for the more active legs of our excursion.