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Uniqlo AIRism Ultra Seamless Boxer Briefs vs Smartwool Active Merino Boxer Brief

The Uniqlo AIRism Ultra Seamless is a synthetic, fully seamless boxer brief built for hot weather, quick drying and a smooth fit under clothes. The Smartwool Active Merino is a merino-blend piece with flatlock seams, temperature regulation and odor resistance, and reviewers rate its fabric and stitching highly. Buy Uniqlo for everyday wear in heat and for a no-seam feel; buy Smartwool for travel, cold-weather base layers and multi-day wear where wool's odor control matters.

  • Choose the Uniqlo AIRism Ultra Seamless if you want a cool, quick-drying, completely seamless brief for daily wear and hot climates.
  • Choose the Smartwool Active Merino if you want merino's temperature regulation and odor resistance for travel, hiking or cold-weather layering.

Prices

  • Uniqlo AIRism Ultra Seamless Boxer Briefs: $14.68 at eBay (last seen Nov 8)
  • Smartwool Active Merino Boxer Brief: $26.55 at eBay (last seen Nov 8)
  • Difference: the Uniqlo AIRism Ultra Seamless Boxer Briefs is $11.87 cheaper than the Smartwool Active Merino Boxer Brief at the latest prices (Nov 8)
Uniqlo
Uniqlo AIRism Ultra Seamless Boxer Briefs

Uniqlo AIRism Ultra Seamless Boxer Briefs

$14.68at eBayChecked Nov 8
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Pros
  • Fully seamless, so no chafe points
  • Cool Touch and quick-dry fabric suit heat
  • Strong two-way stretch holds shape
  • Wide size range up to 3XL
Cons
  • No odor resistance like wool
  • Cannot be tumble dried
  • All-synthetic fabric may feel less natural
Smartwool
Smartwool Active Merino

Smartwool Active Merino Boxer Brief

Smartwool Active Merino

5(68 ratings)
$26.55at eBayChecked Nov 8
See all prices and details
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Store links may earn us a commission.

Pros
  • Merino blend regulates temperature and resists odor
  • Reviewers praise fabric and stitching quality
  • Flatlock seams stay clear of sensitive areas
  • Good for travel and full-day outdoor work
Cons
  • No fly, which some owners dislike
  • Wool blend needs careful washing
  • Narrower size range than A

What separates them

Uniqlo AIRism Ultra Seamless Boxer BriefsSmartwool Active Merino Boxer Brief
Fabric71% polyamide, 29% elastane synthetic blendMerino wool blend with recycled content
Seam constructionCompletely seamless, no sewingFlatlock seams placed away from sensitive areas
Moisture and odorQuick-drying DRY fabric, no odor control claimedMoisture-managing and odor-resistant wool
Temperature feelCool Touch function for hot weatherTemperature-regulating for cold and variable conditions
StretchExcellent two-way stretchElastane content gives stretch but less than A
CareMachine wash up to 40C, no tumble dry, no dry cleanWool blend needs gentle care to avoid shrinkage
Sizing rangeS to 3XLS to 2XL
FlyNo fly mentionedReviewers note there is no fly

Price history

$120.00$14.90
Nov 1Nov 10
  • Uniqlo AIRism Ultra Seamless Boxer Briefs: lowest $14.90 on Nov 9 at UNIQLO; $14.90 on Nov 10.
  • Smartwool Active Merino Boxer Brief: lowest $27.60 on Nov 10 at Wanderlust Outfitters.

Prices at every store

Uniqlo AIRism Ultra Seamless Boxer Briefs

  • UNIQLONew

    In stock

    $14.90+ $7.99 shippingChecked 10 h ago
    Visit UNIQLO
  • eBayNew

    Availability unknownReturns: Set by the eBay seller; the eBay Money Back Guarantee covers an item that doesn't arrive or isn't as described.

    $14.68+ $5.68 shippingChecked Nov 8
    Visit eBay
  • eBayPre-owned

    Availability unknownReturns: Set by the eBay seller; the eBay Money Back Guarantee covers an item that doesn't arrive or isn't as described.

    $15.00+ $6.99 shippingChecked Nov 8
    Visit eBay

Store links may earn us a commission. Some prices via Klarna.

All 2 stores and price history →

Smartwool Active Merino Boxer Brief

  • eBayNew

    Availability unknownReturns: Set by the eBay seller; the eBay Money Back Guarantee covers an item that doesn't arrive or isn't as described.

    $26.55Free shippingChecked Nov 8
    Visit eBay
  • Wanderlust OutfittersNew

    Availability unknown

    $27.60Checked 12 h ago
    Visit Wanderlust Outfitters
  • ChaarNew

    Availability unknown

    $35.00Checked 12 h ago
    Visit Chaar
  • Moss Mountain OutfittersNew

    Availability unknown

    $35.00Checked Nov 1
    Visit Moss Mountain Outfitters

Store links may earn us a commission.

All 15 stores and price history →

Specs compared

SpecUniqlo AIRism Ultra Seamless Boxer BriefsSmartwool Active Merino Boxer Brief
Material composition71% Polyamide, 29% Elastane56% Merino Wool
Available sizesS-3XL—
Care temperatureMachine wash up to 40 degrees, gentle cycle—
Tumble dryingNot suitable for tumble-drying—
Dry cleaningDo not Dry Clean—
StretchExcellent 2-direction stretch—
Fabric functionsquick-drying DRY and Cool Touch functions—
ConstructionCompletely seamless design without sewing—
Fit—Slim fit
Seam construction—Flatlock seam construction
Waistband—Wide elastic waistband
Front panel—Double front panel
Show all 26 specsShow fewer specs
SpecUniqlo AIRism Ultra Seamless Boxer BriefsSmartwool Active Merino Boxer Brief
Material—Polyester
Silhouette—Boxer Brief
Size Type—Regular
Pattern—Solid Color
Size (Small-Large)—M, XL, L, S
Wool (%)—82
Color—Brown
Elastane/Lycra/Spandex (%)—19
Gender—Female
Waist—High Waist

What reviewers say

Uniqlo AIRism Ultra Seamless Boxer Briefs

Owners rate these highly for comfort in heat and for the smooth, seam-free feel under clothing. The recurring gripes are a thin fabric that loses shape after many washes and a fit that runs close, so some size up.

What people mention
  • Seamless comfortPraisedOwners say the lack of seams stops rubbing under trousers and during exercise.
  • CoolingPraisedThe cool-touch, quick-dry fabric is the main reason buyers reach for these in summer.
  • FitMixedMany like the close, second-skin fit, but others find it runs small and size up.
  • DurabilityCriticisedSome owners report the thin fabric pilling or losing elasticity after months of washing.

Smartwool Active Merino Boxer Brief

  • 5 / 568 ratings

Buyers rate it 5 out of 5 across 68 ratings and single out comfort, chafe-free seams and durability. Several wear it for full-day outdoor work and praise temperature control. The most common complaint is that it has no fly.

What people mention
  • ComfortPraisedBuyers describe it as comfortable enough for full days of wear.
  • ChafingPraisedFlatlock seams are credited with preventing chafing on long hikes and work days.
  • DurabilityPraisedOwners report it holds up through repeated use and washing.
Reviews
  • The Best Boxer Briefs for Men of 2026

Questions and answers

Which is better for hot weather?
The Uniqlo AIRism. Its Cool Touch and quick-dry synthetic fabric is built for heat, while the Smartwool is warmer and better suited to cool or variable conditions.
Which lasts longer?
Both hold up well when cared for. The Smartwool's merino blend and stitching draw praise for durability, but wool needs gentler washing; the Uniqlo is easier to machine wash but cannot be tumble dried.
Is the Smartwool worth stepping up to?
Yes if you travel, hike or wear base layers for days and want odor resistance and temperature regulation. For everyday hot-weather wear, the Uniqlo covers it.
Which is better for travel?
The Smartwool. Merino resists odor and regulates temperature, so it handles repeated wear and changing climates better than the synthetic Uniqlo.
Does either have a fly?
The Smartwool does not, and owners list that as a complaint. The Uniqlo is seamless with no fly either.
Which fits better under slim clothing?
The Uniqlo, because it is completely seamless and smooth. The Smartwool's flatlock seams are well placed but still present.

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Buying guides that pick them

  • Best men's boxer briefs
  • Best boxer briefs
Age Group—Adult
Lining—Merino Wool
Sportswear Garment—Yes
Size—Size S, Size M, Size L, Size XL, Size 2XL
  • Temperature controlPraisedWearers say it breathes and regulates temperature in varied conditions.
    • A reviewer's verdict
    • GearLab

      An absolute winner among the boxer briefs tested, thanks to top-notch fabric and stitching and a minimal design with well-placed seams.

      Read the review