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Smartwool NTS Mid 250 Crew Review

Long Underwear

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Editors' Choice Award
Price:   Varies from $54 - $95 online  —  Compare at 4 sellers
Pros:  Extremely comfortable, warm for the weight, stylish, dries quickly, odor resistant
Cons:  Expensive, limited durability
Editors' Rating:     
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Manufacturer:   Smartwool


The soft merino wool of the Smartwool NTS Mid 250 Crew, made from only the cleverest sheep, is not baaaaaaaad. Lame sheep jokes aside, this top isn't just not bad, it's spectacular. We are impressed with its warmth, breathability, and drying speed, but most significantly, its comfort, which is why it wins our Editors' Choice award. This shirt plain feels good. The fabric is light and cozy with a gentle stretch that forms to any movement. Its comfort is combined with handsome styling and technical advantages that make it equally useful for a date with Eve or Everest. Our enthusiasm is tempered only by a concern for durability, which we echo for all merino wool clothing, but with proper care this shirt should last awhile.

Those that balk at its $95 price tag might consider the Best Buy winning Patagonia Capilene 3 Crew, but for anyone who needs to have the best, it's hard to do better than this base layer.

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Analysis and Hands-on Test Findings

Review by:
Jack Cramer
Review Editor

Last Updated:
March 30, 2015
The balance of warmth, breathability, and comfort found in the Smartwool NTS 250 Crew made it our favorite base layer. While expensive and delicate, the quality construction and thoughtful design are characteristics that will be appreciated by any outdoor adventurer.

Performance Comparison

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Drew Smith traversing snow in the Smartwool NTS Mid 250 Crew on the north face of Peak 13,134 outside Ridgway, CO.


Merino wool clothing is commonly sold using the g/m² unit. This convenient practice lets you objectively know the thickness when shopping, and helps consumers compare between brands or to layers they already own. We wish synthetics would be standardized in this way.

At 250 g/m², this top is Smartwool's thickest base layer offered. It is also their most popular. Our testers felt this weight provided an ideal amount of warmth in the moderate temperatures of spring, fall, and winter. During the heat of summer, consider choosing a lighter option like those found in our Best Men's Running Shirt Review.

Overall this top finished in the middle of the pack for this category; not necessarily a bad place to be. Warmer tops we tested often led to overheating, while some of the less insulated brought on a chill during breaks. This middle weight, common to the Smartwool, Icebreaker Oasis, and Patagonia Capilene 3 Crew, is our favorite for cool, cold, and frigid activities.


Like the rest of the merino wool long underwear in this review, this top is exceptionally breathable. We give credit for this performance to the advantageous properties of natural fibers. Water vapor from the skin passed through the fibers without condensing, as advertised.

The 250 g/m² fabric is 50 g/m² heavier than the Icebreaker Oasis, but surprisingly, our testers did not notice a significant decrease in breathability. See the Drying Speed section for a possible explanation. The Smartwool weighs 0.5 ounces more overall.

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Air breezes through the NTS 250 Crew just like Drew Smith breezes through the air; seen here after a long fall while mixed climbing near Ouray, CO.

The simple crew design does limit venting when compared to the long zipper neck of the Patagonia Capilene 4 Expedition Weight 1/4 Zip Hoody, but the Smartwool is a more stylish shirt for urban occasions. During exercise, some heat can be released by rolling up the sleeves; which stay in place well without constricting via the elasticity of woven wool.

Drying Speed

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These sheep are smart: the NTS 250 Crew was quick to dry.
This base layer performed well in our air dry test, placing third, just behind the 30% lighter Under Armour Base 2.0. Curiously, this also placed it ahead of its closest overall competition, the lighter, thinner, Icebreaker Oasis; a result we do not yet have a definitive explanation for. One possibility is the more stretchy fabric of the Smartwool is less densely woven, allowing more air to pass through, and helping it to dry at a faster rate. Another could be a wool surface with more stray fibers to increase dryable surface area. Whatever the actual reason, we were impressed.

During the test we were also impressed with this top's resistance to absorb moisture. Testers had to agitate the material, and all the merino wool layers, underwater before they would become completely saturated. There seems to be some truth to advertisers' claims that merino wool can absorb up to 30% moisture by weight before feeling wet.

Layering Ability

We really like the elasticity of this shirt for its use as a next-to-skin layer. It helps the top to stay in place and form to movements even when insulating layers on top were acting to displace it. This elasticity also allows it to be worn as an insulating layer itself, stretching to fit over a separate shirt. These dual uses mean that it can be worn comfortably across a wide range of temperatures or activity levels.

The crew neck does restrict ventilation options when employed as an insulating layer in medium to high intensity outings. If this is a problem, it is also available in a zip-neck design. For the functional base layer that can release heat the best for start and stop activities, you should consider the Patagonia Cap 4 Hoody.


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A comparison of the sleeve stitching on the Smartwool NTS Mid 250 Crew (tan), Patagonia Merino 2 Lightweight Henley (striped blue), and Icebreaker Oasis (solid blue). All were equally durable, but the Smartwool was the most comfortable.
All of the merino wool layers were plagued by questions of durability. Being such expensive clothing, we would really like it to last. Unfortunately, though, comparable synthetic tops are just more resistant to punctures and abrasion. Smartwool has made a nice garment with quality in design and stitching, but there are limitations to the fabric.

A subtle upside for merino wool in durability is its natural anti-bacterial qualities and a resistance to absorb moisture. These attributes mean that it will not develop unpleasant odors like synthetics; leading to less cycles through the washing machine, an extended life, and happier hiking companions.

One tester suspected that the looser weave on the Smartwool fabric would cause it to wear out faster than the more tightly woven Icebreaker. They even argued that this characteristic should give the Icebreaker the Editors' Choice award instead. We tried our best to substantiate this speculation but we were unable to. In our tests the two shirts appeared comparably durable.

Comfort and Fit

The most outstanding quality of the NTS 250 Crew is its comfort and fit. More than any other long underwear reviewed, this top begged to be worn. Its merino wool was one of the softest fabrics overall, and the sensible design left our testers with no complaints. The length of the waist is just a bit longer than other tops with a slight curve in back to hide a plumber's crack.

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The horizontal seam on the back of the Icebreaker Oasis (blue) vs. the curved stitching on the Smartwool NTS Mid 250 Crew (tan).

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Drew Smith attempting a new route near Ouray, CO. The NTS 250 Crew, which he is wearing beneath, stretches just as well as his legs.
The Icebreaker Oasis came close to matching the NTS 250 Crew in comfort and fit, but lost in this category, and the overall review, due to just a few finer points. The more elastic weave of the Smartwool material helped it conform to the body better, following movements, and rising up less. Stitching patterns on the shoulder and back of the NTS 250 Crew also created less irritation than the Icebreaker when carrying a heavy pack. These minor details don't make the Icebreaker a bad long underwear top, they just separated it from the Smartwool, in what was a very close race.

Best Applications

Apart from the high temps of summer, this top has few situations where it could not be used. Its most ideal use is serving as a true base layer in cold weather activities; where its delicate construction is protected from scrapes by extra layers on top. It is equally functional (and fashionable) at a dinner party as at an unplanned bivy. Consider taking it along on an overseas vacation where laundry might be hard to come by, because its resistance to odors keeps it socially acceptable between belated washes. A UPF rating of 50+ makes it an option for rare situations with extreme sunlight, like days on the water or snow, or at high altitudes.


Street price for this base layer is $95; slightly higher than the Icebreaker Oasis and the second highest overall. We do think the performance it provides justifies the cost. Keep in mind that for outdoor uses you only need one base layer. If you treat it kindly, and don't overwash, this shirt should last for a long time.


There are several stand-out features that helped this long underwear top take home our Editors' Choice award—warmth, breathability, and comfort come to mind—but overall it was the total combination of these qualities into one shirt that brought it out on top. Discerning shoppers should also consider the similar Icebreaker Oasis and the other award winning base layers, the Patagonia Capilene 4 Hoody and Capilene 3 Crew, for particular uses or personal preferences.

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Soaking in the view but not a sunburn with the UPF 50+, Editors' Choice, Smartwool NTS Mid 250 Crew. Zion N.P., UT

Other Versions and Accessories

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Smartwool NTS 250 Crew - Women's
  • Top Pick Award Winner!
  • Women's cut crew neck
  • $95

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NTS mid 250 zip and NTS mid 250 zip - Women's
  • Same great seamless design with a quarter length zippered neck
  • $110

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NTS Mid 250 bottom and NTS mid 250 Bottoms - Women's
  • Same 250 g/m2 weight for your legs
  • $95
Jack Cramer

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OutdoorGearLab Member Reviews

Most recent review: March 30, 2015
Summary of All Ratings

OutdoorGearLab Editors' Rating:   
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Rating Distribution
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5 star: 100%  (1)
4 star: 0%  (0)
3 star: 0%  (0)
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1 star: 0%  (0)

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