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

Men's sizes: Small = 29-31" waist 36-38" hip. Medium = 32-34" waist 39-41" hip. Large = 35-37" waist 42-44" hip. X-Large = 38-40" waist 45-48" hip. XX-Large = 41-44" waist 49-51" hip.

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. Covered elastic waistband, traditional fly, and flatlock seaming to minimize chafing.