Smartwool's heaviest line, Midweight, is perfect for forays into alpine environments where temperatures -- and schedules -- fluctuate. 100% merino wool, interlock knit, UPF 50+.

Women's sizes: X-Small = size 2, 24-25" waist, 32-33" chest. Small = size 4-6, 26-27" waist 34-35" chest. Medium = size 8-10, 28-30" waist 36-38" chest. Large = size 12-14, 31-32" waist 39-40" chest. X-Large = size 16, 33-34" waist 41-42" 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.