Woolpower Thermal Men’s and Women’s Long Underwear Our selection of Woolpower’s long underwear includes both men’s and women’s in a variety of sizes and colors. These long johns are made of the same top quality Merino wool used in Woolpower shirts.  This circular knit fabric provides the perfect balance of breathability and comfort needed in log building, timber framing, and other outdoor activities.  Woolpower’s 200g base layer is designed to keep you warm in temperatures ranging from -4 degrees F to 50 F.  And if you need that extra insulation, check out the mid-layer long underwear garments for sub-zero temperatures and lower activity levels. Enjoy free shipping on all of our thermal wear!