Merino wool is exceptional for performance outdoor wear because the fabric is excellent at regulating body temperature by keeping you warm on cold days and cooler on warm days. It has an excellent warmth-to-weight ratio compared to other wools, in part because the smaller fibers trap body heat. It draws moisture (sweat) away from the skin to provide excellent moisture management, the wool fiber absorbs and releases 10X the moisture of synthetic fibers. The extrafine fibers of Merino wool offer comfortable, no shrink next-to-skin layering without itch or odor.