Icebreaker's Skin 200 Mondo Zip
Skin 200 Mondo Zip (courtesy, Icebreaker)
Gear Guy

What are your thoughts on merino wool base layers?

I’ve been hearing a lot about merino wool base layers, such as Icebreaker. What are your thoughts on this fabric? Is it a suitable alternative to synthetic fleece layers for a mountain climb such as Kilimanjaro? Iain Solihull, UK

Icebreaker's Skin 200 Mondo Zip

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Yes! Wool! Count me in the pro-wool camp. Of course, I always have been. Way back when, before there was an REI on every corner, and the one and only REI stood as a big drafty barn of a building on Seattle’s Pike Street, way back then, one of the most prized items to be found were Air Force surplus “summer uniform” woolen pants. They were light, comfortable across an astonishing temperature range, and windproof enough to be worn as a single lower layer when climbing Mount Rainier. I think they were $5.

Icebreaker's Skin 200 Mondo Zip

Icebreaker's Skin 200 Mondo Zip Skin 200 Mondo Zip

But the wool worn today is far better than those rare Air Force trousers. Icebreaker ( products, for instance, are made from merino wool, which is exceptionally soft and itch-free. Plus, there are little natural pores in the fiber that help add insulation, while also allowing wool to absorb a great deal of moisture before it feels wet. Merino wool also is durable, and, like the pants I recall so well, it’s comfortable across a wider temperature range than synthetics.

I have three Icebreaker shirts of various weights and sleeve lengths. I use them mainly as a base layer for winter bicycling, skiing, and climbing high peaks such as Rainier. Ibex ( and SmartWool ( also make excellent wool-based apparel. For warm weather I still tend to prefer Patagonia’s Silkweight Capilene ( and shirts made from CoolMax (available at stores such as L.L. Bean and REI).

Anyway, when wearing a wool base layer, I need about half the total clothing of other people I’m with. And I don’t need to constantly adjust my layers; I can go with a base layer and maybe a light shell.

The one downside to woolen clothing is its price. Icebreaker’s very useful Skin 200 Mondo Zip—a long-sleeve shirt in a light wool material—is $68. Other pieces are more. That compares to $30 to $40 for most synthetics. But, is it worth it? Overall, I’m inclined to say yes. That goes for your Kilimanjaro climb as well. You don’t need to pack a half-dozen woolen pieces, but two or three—maybe a lightweight tee and a mid-weight, long-sleeve shirt and bottoms —would certainly be useful.

Good luck!

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From Outside Magazine, April/May 2021
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Lead Photo: courtesy, Icebreaker