Product: FieldCore Merino Wool 100% Long Sleeve, Size M FieldCore Merino Wool 100% Long Underwear (with fly), Size M Merino wool is the highest quality wool, a natural material obtained from Merino sheep. The difference from other wools is its excellent moisture absorption, heat retention, and temperature regulation, making it comfortable to wear not only in winter but also in spring and autumn. In addition, it has excellent antibacterial and deodorizing effects, and because the fibers are particularly fine and soft, it is less likely to feel itchy and has a gentle touch. Ideal for mountain climbing, snowboarding, golf, and more!