The Arc'teryx Proton FL Hooded Insulated Jacket provides an excellent balance between air permeability and thermal protection when you're alpine or rock climbing through the warmer months. Its Fortus Air 20 fabric offers light wind-resistance while still allowing air to pass freely so you don't get overheated. Its Octa Loft insulation is breathable and still keeps you warm in those cool alpine temperatures. Designed with climbing in mind, the Proton FL features zippered chest pockets that are easily accessed while wearing a harness. Additionally, the dual hem adjustments keep the jacked tucked under your harness while you reach for high holds. And weighting in at under 10oz, the Proton FL keeps you fast and light on your alpine and climbing adventures.