The Aerotherm Jacket is an exceptionally lightweight, highly breathable mountain windshell jacket with great mobility and excellent breathability, ideal for tackling classic alpine ridges, distant peaks or a breezy peak district crag. These jackets are light, stretchy, windproof, lightly insulated, and compact - they can be worn as an outer layer or as a midlayer under a shell in wet conditions. They are great for running, hiking, and backpacking all year round. Aerotherm Jacket - Men's Softshell