The Icebreaker 300 MerinoFine Polar Women's LS Half Zip is the brand's warmest merino base layer top, made for the coldest days. Ultrafine merino in a heavy, brushed knit delivers plush softness and serious warmth, with a half zip for on-demand venting. It is the deep-winter foundation top for skiers who chase the cold.

Why we like it:

The brushed polar interior is genuinely cozy; it traps a lot of warmth while the ultrafine MerinoFine wool feels soft against the skin. A half zip adds venting so the warmest base layer still breathes when you work.

Features and Functions:

The 300 MerinoFine Polar Half Zip uses a heavy 300 gram merino knit of ultrafine 15.5 micron MerinoFine fibers, brushed for a plush polar interior, with a half-zip collar. The natural wool insulates even when wet, wicks moisture, and resists odor.

Fit and Sizing:

A close fit sits against the skin and layers under a shell. True to size, cut for maximum warmth with easy venting.

Bottom Line:

As the warmest merino base layer top for deep cold, the 300 MerinoFine Polar Half Zip is best at maximum all-natural warmth with easy temperature control. The top to reach for on the coldest days.