Polar Long Johns wool underwear for men from Tufte is our warmest still longs, suitable for expeditions, hunting and more extreme cold, and will keep you warm even during low activity. It is naturally technical and has two layers of 100% merino wool - an inner layer of wool mesh and an outer layer of wool rib. 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 Tuftes Polar Long Johns under a wind and waterproof outer layer for excellent warmth.