The body's ideal core temperature is 37.5°C, and the skin's ideal relative humidity is 37.5%. Patented active particles embedded in the merino wool blend of this sweater help maintain both numbers. When you're hot, they remove sweat in the vapor stage before liquid sweat forms, and when you're cold, they trap energy to help warm you up. The 37.5 polyester technology won't wash out and lasts as long as the sweater does. Cut with a regular fit and set-in sleeves, it's finished with a tubular hem and ribbed neck trim and cuffs.