Icebreaker's versatile, go-anywhere shirt made from breathable 100% merino wool jersey, the 200 Oasis Long Sleeve Crewe is our best-selling base layer top. This ultra-light shirt is designed to keep you cool in the summer and warm in the winter, offering the perfect temperature regulation.

Icebreaker's versatile, go-anywhere shirt made from breathable 100% merino wool jersey, the 200 Oasis Long Sleeve Crewe is the best-selling base layer top.

The ACTIVE WARM ECO KIDS Long-Sleeve base layer top will keep your kids warm and comfortable on any action-packed winter adventure.

With its advanced thermoregulation and soft feel, this multifunctional base layer provides optimal insulation while allowing for a full range of movement. 

An all-season favorite, the Classic All-Season Merino Base Layer Long Sleeve can be sported as a base layer in the fall or summer when it's time to go backpacking.

This base layer features Core Spun technology—which features Merino wrapped around a nylon core for added durability while still keeping the comfort of ultra-soft, responsibly sourced Merino next to skin.

Smartwool's Raglan sleeves eliminate shoulder seams for perfect comfort under a pack, and smooth merrow stitching wraps from side to front to keep you looking as good as you feel.

A heavyweight merino base layer top designed to help regulate temperature during high-intensity activity, the 260 ZoneKnit™ Long Sleeve Half Zip feature 100% pure and natural merino wool.

Meet the new and improved Women's Merino 250 Base Layer Crew.

Smartwool have updated this 100% Merino wool fan-favorite with an enhanced fit to improve functionality while elevating aesthetics. The addition of shoulder panels its flatlock seam construction helps prevent chafing and increases your comfort level.

Add one of Smartwool's best base layers for cold weather to your winter wardrobe and experience the difference the next time you go skiing, hiking, climbing, or biking.

Smartwool have updated the fit of their Men's Classic Thermal Merino Base Layer 1/4 Zip to improve functionality while also enhancing aesthetics.

As one of their heaviest base layer tops and best base layers for cold weather, this garment uses 100% responsibly sourced Merino wool, shoulder panels, and a flatlock seam construction to help minimize chafing as well as help keep you comfortable and temperature regulated as you enjoy high-intensity skiing, hiking, running, and more.

Meet the better-than-ever Men's Classic Thermal Merino Base Layer Crew.

Smartwool have updated this 100% Merino wool fan-favorite with a new fit to improve functionality while enhancing aesthetics. Shoulder panels eliminate top shoulder seams and a flatlock seam construction helps prevent chafing.

Add one of Smartwool's best base layers for cold weather to your winter wardrobe and experience the difference the next time you go skiing, hiking, climbing, or biking.