Hopefully your mom already told you not to wear cotton in the snow. Beyond that, what makes a quality base layer? A few key rules a good pair of long-underwear must follow: wick away sweat and dry quickly; insulate your body heat; move like a second skin; and not smell like rotten cabbage after a week of use. For those of us who don’t shower every day, merino wool, with its natural anti-bacterial properties that keep the garment odor-free, is the most functional (and pricey). They’re basically really expensive underwear, but this layer—keeping you warm in the cold and cool in the warm—is essential to everything we do outside.

Reviews by Julie Brown and Sierra Davis

Trew Chill Top

Duckworth Maverick Snorkel Hoody

Icebreaker Zone Long Sleeve Crew

Voormi Thermal II

Patagonia Merino Air Hoody

Smartwool Women’s NTS Mid 250 Crew

Eider Pila Hoodie

Mountain Hardwear Butterman 1/2 Zip