A base layer is the thin layer you wear against your skin, under your mid layer and jacket. Its job is to keep you warm and move sweat away from your skin. The Classic Thermal crew is Smartwool's midweight merino base layer top, with almost 800 ratings on Amazon.
This review covers why riders pick merino, how long Smartwool base layers last and the quality complaints.
What It Is: A Midweight Merino Top
The crew is 100% merino wool in a midweight knit. Smartwool uses an interlock knit (a tight double knit) for warmth and breathability, and flatlock seams that lie flat to reduce chafing. The fit is slim, so it layers easily under a mid layer.
Smartwool sells a matching bottom in the same fabric.
On the Hill: Warm and Low Odor
The main reason riders choose merino is odor. Riders say synthetic base layers smell bad by the end of the first day, while merino can go several days without picking up much smell. One rider says that alone is worth the extra cost on ski trips.
Not everyone notices a warmth difference. One rider says that most of the time they cannot tell merino from a good synthetic base layer during a day of skiing.
Longevity gets strong praise from some owners. One owner bought three sets of Smartwool base layers over 10 years ago and wears them about 20 times a year for skiing, snowmobiling, running and more. They are surprised at how well they regulate temperature. Another owner says every Smartwool piece they own has outlasted their Darn Tough socks.
Where It Falls Short
Other owners are disappointed with durability. One wore holes in their Smartwool base layers in less than a season, while their old synthetic long underwear has lasted nearly 20 years. Riders point out that pure wool is comfortable but less durable than blends with nylon. Another rider suggests using a wool detergent, because many regular detergents contain enzymes that break down wool.
Consistency is another worry. One owner exchanged a Smartwool thermal shirt for a different size and found the new one thinner and slimmer. The labels showed different countries of manufacture. Amazon lists this crew as made in the USA, so check the label when yours arrives.
Riders also ask whether Smartwool quality has dropped in recent years. Smartwool and Icebreaker have the same parent company, VF Corporation. Some riders say REI's own merino base layers are as good for less money. Other riders still prefer Smartwool over Icebreaker.
Who Should Buy It
Buy the Classic Thermal crew if you want a warm merino top that stays fresh over a multi-day trip.
Look elsewhere if you are hard on clothes and want maximum durability. A merino and nylon blend, or a synthetic base layer, will last longer for less money.
Alternatives
The Smartwool Classic Thermal Merino Base Layer Bottom is the matching midweight bottom.
Verdict
The Smartwool Classic Thermal crew is a warm, low-odor merino base layer that some owners have used for over a decade. Others wore holes in theirs within a season, and quality can vary between shirts. Wash it gently with a wool detergent, and it is a good pick for multi-day trips.
