Men's Classic Thermal Merino Base Layer Crew
Smartwool

Men's Classic Thermal Merino Base Layer Crew

Smartwool's warmest everyday Merino crew, with shoulder panels that take the seam off your pack straps.

$125
Color: Black
Also inWomen'sUnisex
Size:
Size guide
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Top features
100% ZQ Merino wool
Moisture management
Midweight 250 g/m² interlock knit
Description

Meet the better-than-ever Men's Classic Thermal Merino Base Layer Crew. We've updated this 100% Merino wool fan-favorite with new colors and a new fit to improve functionality while enhancing aesthetics. Shoulder panels eliminate top shoulder seams and a flatlock seam construction helps prevent chafing. Add one of our best base layers for cold weather to your winter wardrobe and experience the difference the next time you go skiing, hiking, climbing, or biking.

Perfect for
Ski and ride
Under a shell.
Hike and climb
Cold-weather days.
ZQ Merino
Certified wool.
Features
  • 100% ZQ Merino wool. Smartwool sources this fabric through the New Zealand Merino Company's ZQ programme, which covers animal welfare, environmental and social standards.
  • Moisture management. Merino moves moisture as vapor before it becomes sweat on the skin, so you stay drier under a midlayer on start-stop days.
  • Midweight 250 g/m² interlock knit. The Classic Thermal weight — built for cool to cold weather rather than high-output summer use.
  • Shoulder panels, no top shoulder seam. Shoulder panels remove the seam from the top of the shoulder, where a pack strap bears down all day.
  • Offset seams that wrap to the front. Flatlock construction with offset shoulder and side seams keeps hard edges away from the places a pack or harness rubs.
Size & Fit
Slim
Regular
Relaxed

Close to the body. Size up if you're between sizes or want room to layer underneath.

Slim fit, intended to follow the contour of the body. Take your usual size for a close base-layer fit; size up if you want more room through the body or plan to layer underneath. Shoulder panels eliminate the top shoulder seam and the side seams are offset and wrap to the front, so nothing hard sits under a pack strap.

Open size guide
Materials
  • 100% Merino wool.
  • Care: Machine wash cold on gentle cycle with like colors; do not bleach; tumble dry low or lay flat to dry; do not iron; do not dry clean.
About the brand

Smartwool brings the magic of merino wool to life — keeping you warm, dry, and comfortable no matter the season. From performance socks to base layers, every piece is designed for adventure. At Mountain Sports, we love Smartwool because it proves comfort and sustainability can go hand in hand, from trail to town.

Shop all Smartwool

SKU SW016349-001 · Style SW016349
Size guide

Smartwool Size Chart - Men's Apparel

Smartwool Sizing Chart

Measurements are in inches, unless otherwise noted. Charts reflect body measurements, not garment measurements.

Men's Apparel & Base Layers:

Size Chest Waist Hip Arm Length Inseam
S 36 - 38 29 - 31 36 - 38 31 - 32 30 - 31
M 39 - 41 32 - 34 39 - 41 32 - 33 31 - 32
L 42 - 44 35 - 37 42 - 44 33 - 34 32 - 33
XL 45 - 48 38 - 40 45 - 48 34 - 35 33 - 34
XXL 49 - 51 41 - 44 49 - 51 35 - 36 34 - 35

How to measure - Chest: measure under the arms, around the fullest part of your chest and back. Waist: measure around your natural waistline, keeping the tape a bit loose. Hip: measure around the fullest part of your hip, parallel to the floor. Arm length: with your elbow slightly bent, measure from the center back of your neck, across the top of your shoulder, to the elbow and down to the wrist bone. Inseam: measure along the inside of the leg from crotch to ankle bone, or measure a well-fitting base layer pant from the crotch seam to the bottom of the leg.

Smartwool clothing runs true to size. Smartwool products are designed to retain their fit and shape; following the care instructions on the label will help avoid shrinking or stretching.
Performance

How it ranks across conditions.

Calibrated against comparable products we stock, so you can compare like for like.

Warmth

Light
Midweight
Warm
Very warm

At 250 g/m² this is Smartwool's Classic Thermal weight — the warmest of their everyday Merino base layer fabrics, built for cool to cold conditions.

Breathability

Low
Moderate
High
Very high

Merino breathes well for its warmth, but a 250-weight knit is denser than a 150 — expect to run warm on high-output days above freezing.

Odor resistance

Low
Moderate
High
Excellent

Merino resists odor build-up naturally, which is what makes a wool crew wearable for several days on a hut trip.

Fit

Compression
Slim
Standard
Relaxed

Smartwool's slim fit follows the contour of the body so it layers cleanly under a midlayer or shell without bunching.

Best for

Is this right for you?

Ski and snowboard days

Smartwool labels this weight start-stop activity, which is exactly what a lift day is. Warm on the chair, breathable enough on the way down.

Not for: For sustained high-output cold-weather effort like skinning laps, Smartwool points to their Intraknit line instead. Pair it with the Classic Thermal Bottom

Cold-weather hiking and climbing

Shoulder panels remove the seam from under a pack strap, and offset side seams keep the rest away from a harness.

Not for: A crew neck cannot be vented. If you run hot and stop and start a lot, a quarter-zip gives you a way to dump heat. Try the Classic Thermal 1/4 Zip

Everyday winter layering

Clean enough to wear on its own under a coat, and odor-resistant enough to go several days between washes on a trip.

Not for: Above about 50°F this is more wool than most people want against the skin all day. Try the lighter Merino 150 Long Sleeve

Full spec sheet

Technical Specs

Material100% Merino wool, exclusive of decoration
Fabric weightMidweight — 250 g/m²
Garment weight276 g (9.74 oz)
FitSlim — follows the contour of the body
NecklineCrew
ConstructionShoulder panels eliminate the top shoulder seam; flatlock seams, offset shoulder and side seams, side seams wrap to front
Certification100% ZQ Merino wool
Country of originMade in Vietnam
Style numberSW016349
Questions, answered

Before you buy.

Pulled from chats, emails and store visits. The things people actually ask us before they buy. Don't see yours?

Ask a question
How does the 250 weight compare to Smartwool's 150?

The 150 (Classic All-season) is a lightweight 150 g/m² fabric Smartwool positions for warm to cool weather — worn alone on warm days, as a layering foundation on cooler ones. This Classic Thermal is 250 g/m² and is made for cool to cold weather. If most of your days are above freezing and high-output, the 150 is the better pick.

Do the shoulder panels actually matter?

Yes, if you carry a pack. Shoulder panels eliminate the top shoulder seam, which is exactly where a pack strap bears down. Offset side seams and flatlock construction keep the rest of the seams away from where a harness or hipbelt rubs.

Do these run true to size?

Smartwool builds this in a slim fit intended to follow the contour of the body, sized to their standard men's chart. Take your usual size for a close base-layer fit; size up if you want more room through the body or plan to wear something underneath.

Will 100% Merino hold up to regular washing?

Yes, with reasonable care. Machine wash warm on a gentle cycle and tumble dry low or lay flat. Skip fabric softener — it coats the fiber and blunts the wool's moisture management. Merino also needs washing far less often than synthetic, so it sees the machine less to begin with.

What does ZQ certified wool mean?

ZQ is a wool certification developed by the New Zealand Merino Company, covering animal welfare, environmental management and social standards on the farms that supply the fiber. Smartwool states that practices which cause harm, such as mulesing, are never permitted under it.

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