Smartwool Men's Intraknit Thermal Merino Base Layer Bottom
Smartwool Men's Intraknit Thermal Merino Base Layer Bottom
Smartwool Men's Intraknit Thermal Merino Base Layer Bottom
Smartwool Men's Intraknit Thermal Merino Base Layer Bottom
Smartwool Men's Intraknit Thermal Merino Base Layer Bottom
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Men's Intraknit Thermal Merino Base Layer Bottom

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Men's Intraknit™ Thermal Merino Base Layer Bottom

Start your layering system with our most innovative foundation to date; our Intraknit™ collection. Our Men's Intraknit™ Thermal Merino Base Layer Bottom puts warmth first, while seamlessly knit mesh ventilation helps keep you dry and comfortable. Our revolutionary 3D mapping provides maximum mobility so nothing slows you down. Gear up to take on any weather with these men's Merino wool pants.

Intraknit™ 3D-Knit Thermal Construction
Intraknit™ technology: insulation, articulation, and ventilation are seamlessly integrated to help with movement and comfort. Rather than sewing separate panels onto a base fabric, the Intraknit™ knit builds the insulation, breathability, and stretch zones directly into the fabric itself. The result is a single piece of knit that warms where the body is static, breathes where the body works, and stretches where the body bends — with fewer seams and fewer cold spots than a sewn-together equivalent.
Merino Sport Yarn Blend — Heavyweight
52% Merino Wool, 44% Polyester, 2% Elastane, 2% Polyamide. Merino Sport yarn wraps soft Merino fiber around a durable polyester core — the Merino delivers the natural temperature regulation and odor resistance; the polyester core adds the abrasion toughness and faster dry time a deep-cold-weight base layer needs. 2% elastane gives the 3D-knit articulation the stretch recovery across the hip, knee, and ankle.
Heavyweight — Built For Deep Cold
Heavyweight positions this bottom as the right choice for sub-freezing days, lift-served skiing, ice climbing, mountaineering, and long static belay sessions — not shoulder-season high-output activity. Warmer than the All-Season Intraknit bottom, heavier than the midweight Classic Thermal 250g/m². The right weight when a midweight would soak through before lunch on a -10° lift ride.
Seamlessly Knit Mesh Ventilation
Seamlessly knit mesh ventilation — the breathability is built into the knit itself rather than added as sewn-on mesh patches. Heavy warmth with high-output breathability in a single fabric, no glued-in ventilation strips, no bulky seams that cold-spot or wear through. The mesh knit breathes where the body needs it and insulates where it doesn't.
3D Mapping For Near-Custom Fit & Movement
3D mapping results in near custom fit and freedom of movement. The knit is tailored to the body's natural articulation points — it relaxes where the leg bends (hip, knee, ankle) and compresses where the leg is straight (quad, calf). Fewer hot spots at the articulation points, less bunching under outer layers, and a base layer that moves with the body rather than fighting it.
Mid-Rise Waist
Fitted with a mid-rise waist that sits between a low-rise hip-hugger and a high-rise waistband — the right rise for layering under hiking pants, ski pants, or snow bibs without the waistband rolling down at the hip or digging in at the rib. The mid-rise also keeps the base layer covered when the jacket or shell rides up on a steep descent.
Men's-Specific Slim Fit — Inseam 28.75" (Size M)
Our slim fit is intended to follow the contours of the body without excess bulk. Engineered in men's proportions — broader through the hip and thigh, with a 28.75" inseam on a size medium that hits at the right spot above the ski-boot cuff. Layers cleanly under hiking pants, ski pants, or running tights without bunching at the knee or ankle.
Multi-Activity Versatility
Built for the wide range of deep-cold activities where warmth is the priority but high-output movement still demands breathability — alpine touring, ice climbing, lift-served skiing, mountaineering, winter trail running, and backcountry hut trips. The Merino Sport yarn blend handles the cold-to-warm swings without the clammy chill a pure synthetic would develop when you stop moving.
Technology
Intraknit™ 3D-Knit (Insulation, Articulation, Ventilation); Merino Sport Yarn; Body-Mapped Ventilation

General

Product
Men's Intraknit™ Thermal Merino Base Layer Bottom
Fit
Slim fit (intended to follow the contours of the body)
Category
Thermal Base Layer Bottom (Heavyweight, 3D-knit)
End Use
Deep-Cold Activity, Winter Layering
Technology
Intraknit™ 3D-knit (Insulation, Articulation, Ventilation zones); Merino Sport yarn; Body-Mapped Ventilation
Gender
Men's
Available Sizes
S, M, L, XL, XXL

Materials & Construction

Fabric Weight
Heavyweight (Thermal — built for deep cold)
Fabric Composition
52% Merino Wool, 44% Polyester, 2% Elastane, 2% Polyamide. Exclusive of Decoration.
Knit Construction
3D-knit Intraknit™ — body-mapped insulation, articulation, and seamlessly knit mesh ventilation
Waistband
Mid-rise waist
Inseam
28.75" (73 cm) on size medium
Seam Construction
Minimal seams (3D-knit construction eliminates most traditional seam lines)
Country of Origin
Made in India
Washing
Machine wash cold on a gentle cycle. Wash with like colors — the Merino Sport blend benefits from isolated washing to protect the fabric's thermal and moisture-management properties. Cold water protects the elastane recovery and the Merino Sport yarn's polyester core. Use a mild, technical wash; avoid fabric softeners.
Drying
Dry flat. Do not tumble dry. The heavyweight Intraknit 3D-knit retains its body-mapped ventilation and insulation structure best when laid flat to dry — tumble heat can flatten the knit's articulation zones at the hip and knee, and shrink the Merino fibers. Lay flat on a clean towel away from direct heat.
Bleach & Iron
Do not bleach. Cool iron as needed — do not iron decorations. Bleach breaks down Merino wool fibers and degrades the elastane. Iron only on low heat and only on the non-decorated fabric areas; high heat can scorch the Intraknit™ 3D-knit structure and flatten the body-mapped ventilation zones.
Dry Cleaning
Do not dry clean. The harsh solvents used in commercial dry cleaning strip the natural lanolin from Merino and degrade the Merino Sport yarn's polyester core — both of which are core to the fabric's thermal and moisture performance.
Storage
Store folded in a dry, breathable space. Merino Sport yarn resists odor naturally — the same bottom covers multiple wear days between washes, which extends the fabric's lifespan. Folded storage preserves the 3D-knit structure; hanging for long periods can stretch the elastane out of the articulation zones at the hip and knee.

Shipping Policy

Components:

All component items (wheels, drivetrains, suspension, brakes, etc.) ship within 4-7 business days of purchase.

Bicycles:

Complete bikes typically ship within 2–3 weeks due to build, tuning, and inspection times. You will receive tracking information as soon as your order is ready to ship.

Riding Gear & Apparel:

Riding gear and apparel orders (helmets, jerseys, gloves, etc.) ship within 3-10 business days.

Returns & Exchanges:

If you received the wrong size or wish to exchange an item, it must be returned in original condition—unused, uninstalled, and with all packaging intact.

For full details, please see our Refund Policy before initiating a return.

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Merino Layer System — SW016829

Built For

Alpine Touring
10° – 30°F
Cold skin-track ascents and sub-freezing descents where a midweight bottom would soak through on the climb and chill on the way down. The heavyweight Intraknit™ insulation retains warmth under a shell when static, and the body-mapped ventilation dumps heat on the skin-track without breaking thermal continuity at the core. The 28.75" inseam layers cleanly above the ski-boot cuff on the descent.
Ice Climbing
0° – 25°F
Long static belay sessions in bitter cold where a lighter bottom would lose core warmth, with high-output swinging bursts where breathability matters. The Merino Sport yarn's polyester core keeps the fabric lofted when wet from ice and breath, and the heavyweight knit holds the heat through the slow minutes between pitches. The mid-rise waist stays put under a harness all day.
Lift-Served Skiing
15° – 35°F
Full chairlift days at the resort when the wind chill is the limiting factor. The heavyweight 3D-knit insulates under a shell on the chair and on cold lift rides; body-mapped ventilation across the upper thigh and behind the knee dumps heat on the groomers without breaking core warmth. The 28.75" inseam hits at the right spot above the ski-boot cuff.
Winter Mountaineering
Sub-Freezing
Multi-pitch winter routes and hut-to-hut trips where the temperature stays well below freezing all day. Heavyweight 3D-knit insulation layers cleanly under a hardshell and a belay parka; the mid-rise waist stays in place under a harness or pack-belt all day. The Merino Sport yarn's abrasion resistance stands up to alpine-grade wear on rough snow and rock approaches.
Layer Over It

Top It With A Shell

The Intraknit Thermal Bottom is the lower half of a complete deep-cold Intraknit base layer system. Layer a hardshell, insulated ski pant, or snow bib over it for full weather protection — the slim base-layer fit doesn't bunch under a ski-pant shell, and the heavyweight 3D-knit holds warmth against a belay parka's compressible insulation.

  • Insulated ski pant or hardshell wind and waterproof outer layer
  • Snow bib deep-snow insulated outer
  • Softshell hiking pant cold-weather active outer
  • Men's Hike PhD™ crew sock full-day cold-weather rotation pair
Layer Under It

Pair It With The Crew

For the complete heavyweight Intraknit system, pair this bottom with the matching Men's Intraknit™ Thermal Colorblock Crew (SW016453). Same 3D-knit construction, same Merino Sport yarn blend, same body-mapped ventilation philosophy — a full-body heavyweight base layer system engineered to work as one piece. The slim fit layers cleanly without bulk under a puffy or a hardshell.

  • Men's Intraknit™ Thermal Colorblock Crew matched heavyweight system
  • Men's Intraknit™ Thermal 1/4-Zip collar-up cold-weather option
  • Men's Smartloft™ crew insulated mid-layer over base
  • Men's Classic Thermal Merino crew warmer-on-the-torso option

Prepared with intention.

Every product is carefully inspected and handled by our team before it ships. From fit and function to final details, we make sure each piece is ready for the outdoors ahead—so you can focus on the experience, not the gear.

Passion drives us

At SpokeX Bike Co., bikes aren't just our business — they’re our way of life. As a rider-owned and operated shop, every decision we make comes from firsthand experience on the trail, at the race, and on the open road. We know what it’s like to chase a new line, push through the pain cave, and celebrate the ride — because we live it every day.


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