Women's Polar Half Zip from Tufte is our warmest woolen underwear in wool mesh, and is suitable for expeditions, hunting and more extreme cold, and will keep you warm even with low activity. Naturally technical, this high-necked zip-up wool jumper features two layers of 100% merino wool - an inner layer of wool mesh and an outer layer of wool ribbing. The two layers are sewn together in panels. The woolen mesh provides super insulation and warmth by trapping small air pockets inside the mesh structure, which are heated naturally by your own body heat. The outer layer absorbs moisture to keep you both warm and dry. In extreme cold, dress in Tufte Polar under a wind and water resistant outer layer or a down jacket for very good warmth.