Game for any adventure, any time of year, the men's Smartwool Classic All-Season Merino quarter-zip base layer top is made from a lightweight jersey and built for comfort—even under your pack.

Underwear TopsBase Layer Tops

Made from premium merino wool, the Smartwool Classic Thermal Merino Crew base layer top helps regulate your temperature with improved performance functionality while hiking or skiing in cold weather.

Underwear TopsBase Layer Tops

Made of heavyweight merino wool, the men's Smartwool Classic Thermal Merino quarter-zip base layer top helps regulates your temperature during high-intensity skiing, hiking or running in cold weather.

Underwear TopsBase Layer Tops

Made of heavyweight merino wool, the men's Smartwool Classic Thermal Merino quarter-zip top helps regulates your temperature during high-intensity skiing, hiking, running and more in cold weather.

Underwear TopsBase Layer Tops

Engineered for the most demanding athletes in the toughest conditions, the men's Artilect Darkhorse 185 Zoned base layer top get you in the zone with lightweight and durable merino wool.

Underwear TopsBase Layer Tops

You can stop looking for that ideal base layer. The tasc Performance Elevation Merino men's T-shirt offers superior temperature regulation and moisture management without the bulk.

Underwear TopsBase Layer Tops

Purpose-built for advanced insulation and unrestricted mobility, the men's NRS Expedition Weight base layer shirt layers seamlessly under drysuits, helping paddlers hit the water in cold conditions.

Underwear TopsBase Layer Tops

As solid and dependable as its namesake rock formation in Colorado, the men's Artilect Flatiron 185 crew is durable yet comfortable and made for effortless, reliable performance in harsh conditions.

Underwear TopsBase Layer Tops

Offering up personalized comfort, the men's Artilect Flatiron 185 Quarter-Zip base layer top gives you warm, fast-drying wool and a zipper that lets you vent or add heat to your core.

Underwear TopsBase Layer Tops

Harnessing the warming power of Heatwave™ technology, the men's Seirus Heatwave Lite Reversible Long-Sleeve base layer top reflects heat back to your body, and is now available in a lighter design.

Underwear TopsBase Layer Tops

Harnessing the warming power of Heatwave™ technology, the men's Seirus Heatwave Reversible Long-Sleeve Crew base layer top reflects heat back to your body to fend off winter's chill.

Underwear TopsBase Layer Tops

Pack less and do more with the men's Mons Royale Icon Raglan top. You'll go from bike laps to alpine climbs and everything in between without having to change shirts.

Underwear TopsBase Layer Tops

With mesh ventilation for cooling, minimal seams to help reduce chafing and a fit that moves with your body, the men's Smartwool Intraknit Active base layer top is ready to go the distance with you.

Underwear TopsBase Layer Tops

With merino comfort, ventilation and articulated flex zones, the Smartwool Intraknit Thermal Max Quarter-Zip base layer top will be what you grab first for high-intensity, cold-weather adventures.

Underwear TopsBase Layer Tops