Smartwool NTS Midweight Crew - Men's 100% Wool Men's sizes: Small = 29-31" waist 36-38" chest. Medium = 32-34" waist 39-41" chest. Large = 35-37" waist 42-44" chest. X-Large = 38-40" waist 45-48" chest. XX-Large = 41-44" waist 49-51" chest. 100% merino wool interlock knit, UPF 50+. Machine wash cold, tumble dry low. Comfortable next to the skin, and offering the world's most efficient moisture-management system. Crew neck with set-in long sleeves. Shoulder panels eliminate top shoulder seams. Flatlock seam construction eliminates chafing.