Like the socks this brand built its reputation on, the Smartwool Merino 150 base layer uses Merino wool – a material that's often used for outdoor apparel, being breathable yet warm, and ...

Fortunately, we’ve got an easy trick to tell which merino wool base layer is right for you. Merino wool base layers, also known as thermal underwear or long underwear, come in various weights ...

but the best base layers are made with a percentage of merino wool (though, they will be pricier). Merino is very warm but still highly breathable and is great at wicking away sweat. It also has ...

(Honestly, the only thing that keeps it from being my go-to base layer to this day is the fact that mine is purple and just doesn’t go with much.) Made with 100-percent merino wool, it’s a ...

Good base layers should be formfitting — not tight but not loose — in order to retain heat. They are often woven from merino wool or technical synthetic fabrics that also have moisture-wicking ...

From natural temperature-regulating fabrics like Merino wool to synthetic options engineered to wick moisture, today’s base layers are marvels of technology. Our test crew put 50 items through ...