Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top review: a super comfortable, high performing base layer

Stylish and versatile, the Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top is an impressive and mega-comfortable, all-merino top

Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top
(Image: © Icebreaker)

Advnture Verdict

A handsome, high-performing piece of kit for all outdoor activities all year round, the Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top is not cheap, but you will seek it out on multiple occasions and it won’t let you down.


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    Super comfortable

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    High performing and odour resistant

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    Keeps working when wet


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    Won’t last as long as synthetic tops

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    No thumb hoops

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First impressions

The Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top is entirely made with merino wool – magic material that keeps you warm when you need it to, but which can also cool you down when conditions are hot (those sheep are smarter than they look).

Kiwi company Icebreaker very early on recognized the potential of this fabric for an outdoor-active audience, and they remain way out in the lead when it comes to producing classy and quality garments made from merino, such as this base layer, which is 100% straight off the sheep’s back.

Icebreaker have never been a cheap brand, and £100 is quite steep for a relatively lightweight and ostensibly basic garment, but the genius of this label isn’t just in the level of performance their gear provides – which is ace – but in the quality of the design. The Oasis long-sleeve thermal top is no exception, and the top features a pattern formed by the pictures of a melting Greenland icecap, captured by New York City–based artist and photographer, Justin Brice Guariglia, who is known for his work addressing climate change. (In case you’re wondering, the dye used is plant-based and ethically sourced.)

A bit of an indulgence, perhaps, for an undergarment – but whatever floats your boat.


RRP: $95–$110 (US) / £75–£100 (UK)
Gender availability: Male / Female
Materials: Merino wool
Weight (male large): 263g / 9.3oz
Sizes: Men: S–XXL; Women: XS–XL
Colors: Men: Black / Midnight navy / Gritstone heather / Estate blue / Nightfall / Polar / Redwood / Cavern; Women: Black / Midnight navy / Fire / Hydro / Redwood / Curry
Compatibility: Hiking, biking, trail running, climbing, alpine adventures

In the field

The weight of the Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top – 200 gsm (grams per square metre) – is pretty much perfect for a base layer that you intend to wear during outdoor activities such as hiking, trail running and cycling, where the moisture-wicking capability of the garment makes it a solid performer. Because merino maintains its thermal properties even when wet, this top can also be worn when canoeing and kayaking. And with merino’s natural antimicrobial odour-resistant properties, you can wear it for several days, on the trail and in your sleeping bag, without the material getting stinky – making it an ideal lightweight high-performing garment for backpacking escapades.

We wore this top on chilly trail running and trekking outings, and during a mid-winter sea paddle, and it performed excellently in all scenarios. The comfort levels of the Oasis are superb, and all the other naturally occurring qualities of merino come into play to make it a dynamic, high-performing piece of underwear.

The lack of thumb hoops is a disappointing omission on a premium-priced piece of kit, though, and it does lead to the sleeves riding up your arms when you put on a mid or outer layer.

Although it’s ideal for keeping you warm in winter and early spring/late autumn, we’ll be wearing this base layer well into the warmer months too, especially during camping trips and when kayaking and canoeing, because the merino material never gets too warm and it’s an ideal long-sleeve top for all seasons.

Pat Kinsella

Author of Caving, Canyoning, Coasteering…, a recently released book about all kinds of outdoor adventures around Britain, Pat has spent 20 years pursuing stories involving boots, bikes, boats, beers and bruises. En route he’s canoed Canada’s Yukon River, climbed Mont Blanc and Kilimanjaro, skied and mountain biked through the Norwegian Alps, run an ultra across the roof of Mauritius, and set short-lived records for trail-running Australia’s highest peaks and New Zealand’s Great Walks. He’s authored walking guides to Devon and Dorset, and once wrote a whole book about Toilets for Lonely Planet. Follow Pat’s escapades on Strava here and Instagram here.