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Smartwool Classic Thermal Merino 3/4 Bottom vs KUIU ULTRA Merino 160 Bottom

The Smartwool Classic Thermal is the warmer, more natural pick: 250 g/m² of pure merino with a 3/4 leg that stops above the boot. The ULTRA Merino 160 is lighter and stretchier, thanks to a Nuyarn merino-polyester blend and a full 28-inch leg, and it has far more owner feedback behind its rating. Buy the Smartwool for cold ski and winter layering, the ULTRA for active hunting and multi-day wear where durability and shape retention matter.

  • Choose the Smartwool Classic Thermal if you want maximum warmth from pure merino and a 3/4 cut that keeps fabric out of your boots.
  • Choose the ULTRA Merino 160 if you want a lighter, full-length bottom that holds its shape over long, sweaty days.

Prices

  • Smartwool Classic Thermal Merino 3/4 Bottom: $105.00 at Miyar Adventures (checked today)
  • KUIU ULTRA Merino 160 Bottom: $89.00 at KUIU (checked today)
  • Difference: the KUIU ULTRA Merino 160 Bottom is $16.00 cheaper than the Smartwool Classic Thermal Merino 3/4 Bottom today
Smartwool
Smartwool Men's Classic Thermal Merino Base Layer 3/4 Bottom

Smartwool Classic Thermal Merino 3/4 Bottom

Smartwool Men's Classic Thermal Merino Base Layer 3/4 Bottom

4.8(128 ratings)
$105.00at Miyar AdventuresChecked 8 h ago
See all prices and details
Visit Miyar Adventures
Pros
  • Pure merino breathes and resists odor without synthetic content
  • Heavier knit holds warmth in cold conditions
  • 3/4 leg avoids bunching inside ski and hiking boots
  • Redesigned fit reduces sag and excess fabric
Cons
  • All-merino interlock can stretch out with heavy use
  • 3/4 length leaves the lower calf exposed
  • Slim fit runs close and may not suit everyone
ULTRA
ULTRA Merino 160 Bottom

KUIU ULTRA Merino 160 Bottom

ULTRA Merino 160 Bottom

4.8(592 ratings)
$89.00at KUIUChecked 8 h ago
See all prices and details
Visit KUIU
Pros
  • Lighter fabric suits high-output activity and layering
  • Nuyarn blend resists stretching and holds shape
  • Full-length leg with gusset and darted fly for comfort
  • Large base of owner ratings praising fit and durability
Cons
  • Less warm than a 250 g/m² layer
  • Polyester content reduces the pure-merino feel
  • Full length can bunch inside tight boots

What separates them

Smartwool Classic Thermal Merino 3/4 BottomKUIU ULTRA Merino 160 Bottom
Fabric weight250 g/m², a warm midweight layer160 g/m², a light layer
Fiber content100% merino wool67% merino, 33% polyester (Nuyarn)
Leg length3/4 length, 20-inch inseam on mediumFull length, 28-inch inseam
Stretch and shape retentionInterlock knit can sag over timeBlend is built to resist stretching out
Odor controlPure merino resists odor wellMerino blend also resists odor
Seams and flyFlatlock seams, merino-covered waistband, traditional flyFlatlock seams, crotch gusset, layered darted fly
Warmth ratingRated warm for 50°F and belowMarketed for cold to frigid conditions
Owner feedback4.8 from 128 ratings4.8 from 592 ratings

Price history

$115.00$89.00
Nov 3Nov 9
  • Smartwool Classic Thermal Merino 3/4 Bottom: lowest $115.00 on Nov 3 at Reeds Family Outdoor Outfitters; $115.00 on Nov 9.
  • KUIU ULTRA Merino 160 Bottom: lowest $89.00 on Nov 9 at KUIU.

Prices at every store

Smartwool Classic Thermal Merino 3/4 Bottom

  • Miyar AdventuresNew

    In stockReturn policy

    $105.00Checked 8 h ago
    Visit Miyar Adventures
  • OMC GearNew

    In stockReturn policy

    $105.00Checked Nov 9
    Visit OMC Gear
  • Ascent OutdoorsNew

    In stockReturn policy

    $105.00Checked Nov 9
    Visit Ascent Outdoors
  • Ascent CyclesNew

    In stockReturn policy

    $105.00Checked Nov 9
    Visit Ascent Cycles
All 14 stores and price history →

KUIU ULTRA Merino 160 Bottom

  • KUIUNew

    In stockReturn policy

    $89.00Checked 8 h ago
    Visit KUIU

Also available at

  • KUIUCheck price at KUIU
Prices and history →

Specs compared

SpecSmartwool Classic Thermal Merino 3/4 BottomKUIU ULTRA Merino 160 Bottom
Fitslim fitFitted Base Layer, 28-inch inseam
Fabric weight250g/m2—
Merino content100% Merino Wool—
Inseam size medium20" (50 cm)—
Waistmid-rise waist—
Country madeVietnam—
Temp ratingWarm 50° +—
Weight—5.9 oz / 167 g (L)
Material—67% Merino Wool / 33% Polyester- 160 g/m²
Inseam Length—28″
Best Use—Base Layer
Protection—Naturally Odor Resistant

What reviewers say

Smartwool Classic Thermal Merino 3/4 Bottom

  • 4.8 / 5128 ratings

Rated 4.8 out of 5 from 128 ratings, owners consistently praise the warmth, softness and odor control of the wool and the boot-friendly 3/4 cut. Complaints center on the slim fit and the care wool demands.

What people mention
  • FitMixedThe slim cut is praised for staying put but some owners find it snug.
  • Odor controlPraisedOwners report wearing it several days without smell.
  • WarmthPraisedReviewers call it warm for its weight without bulk.
  • LengthMixedThe 3/4 cut suits boots but leaves ankles exposed in deep cold.

KUIU ULTRA Merino 160 Bottom

  • 4.8 / 5592 ratings

Buyers rate it highly, calling it soft, lightweight and warm for cold weather. The fit and odor resistance draw the most praise, and owners describe it as high quality and not constraining.

What people mention
  • FitPraisedOwners say it fits well and stays comfortable all day without feeling tight.
  • ComfortPraisedBuyers describe the fabric as soft and not constraining next to skin.
  • WarmthPraisedReviewers say it keeps them warm in cold weather as a base layer.
  • OdorPraisedOwners report it stays fresh over extended wear thanks to the merino.

Questions and answers

Which is warmer for skiing?
The Smartwool. Its 250 g/m² pure merino knit is a midweight layer rated for warm conditions at 50°F and below, while the ULTRA is a 160 g/m² light layer. For cold lift days, the Smartwool is the safer pick.
Which holds up better over time?
The ULTRA. Its Nuyarn merino-polyester blend is designed to resist the stretching and sagging that plain merino knits can develop. The Smartwool's all-merino interlock is comfortable but softer and more prone to losing shape.
Is the 3/4 length a problem?
Not if you wear boots. The Smartwool's 20-inch inseam stops above the boot cuff, which cuts friction and bulk. If you want full leg coverage for standalone wear, the ULTRA's 28-inch leg is the better fit.
Which is better for multi-day hunts?
The ULTRA. It is purpose-built for extended wear, with a lighter knit, a crotch gusset and a blend that keeps its shape. The Smartwool resists odor well too, but it is heavier and less durable under repeated use.
Is the ULTRA worth stepping up to from a basic thermal?
Yes if you want a light, stretchy merino layer with a proven fit. Its 592 owner ratings at 4.8 back that up. If warmth is your priority, the Smartwool is the stronger layer.

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More comparisons

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  • Smartwool Classic Thermal Merino Base Layer Bottom Men's vs ULTRA Merino 160 Bottom

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