Smartwool established a reputation for its high-performance merino wool base layers — offering unbeatable warmth, breathability, and moisture-wicking properties.

　　The brand has since built on the success of its core product with innovations and technologies like Intraknit, which enhances fit, stretch, and moisture management for even better performance.

　　We all want to stay warm and dry during winter pursuits. Knowing which Smartwool layers perform best in certain temperatures and activity levels will help. Below, well walk you through five different base layers, starting with the more advanced pieces and ending with the classics.

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　　(Photo/Smartwool) Intraknit Thermal Max Merino: Built for the Coldest Adventures In short: Combines 100% merino wool with advanced Intraknit technology for unmatched warmth, targeted insulation, and breathability.

　　Tech Features: Smartwool Intraknit Max Thermal Merino Base Layer combines advanced Intraknit technology with 100% merino yarn for superior insulation, moisture management, and thermoregulation. The brands 3D mapping allows for a near-custom fit, with insulating terry loops and mesh ventilation in gender-specific zones for balanced warmth and breathability. Knit-in reflective elements and an 8.25-inch zipper add functionality for high-intensity activities.

　　Temperature Guide: 25°F and below.

　　Intraknit Thermal Max Merino Base Layer 1/4 Zip — Mens

　　(Photo/Smartwool) Shop Now Intraknit Thermal Max Merino Base Layer Bottom — Womens

　　(Photo/Smartwool) Shop Now Intraknit Thermal Merino: Precision Comfort for Versatile Cold-Weather Performance In short: Balances warmth, breathability, and flexibility, with Intraknit technology ensuring a snug fit and strategic ventilation for active pursuits in variable cold climates.

　　Tech Features: Featuring a slim fit with 3D mapping for a near-custom feel, it offers freedom of movement, ribbed elbows for added durability, and engineered knit structures for lighter weight and a cleaner finish. Smartwools Merino Sport yarn blends the natural performance of merino wool with the durability and quick-drying properties of polyester, while mesh ventilation in gender-specific zones ensures optimal comfort and dryness. It weighs just 205 g.

　　Temperature Guide: 25°F and below.

　　Intraknit Thermal Merino Base Layer Crew — Mens

　　(Photo/Smartwool) Shop Now Intraknit Thermal Merino Base Layer Bottom — Mens

　　(Photo/Smartwool) Shop Now Intraknit Active Base Layer: Dynamic Comfort for High-Output Activities In short: Lightweight, breathable, and designed with Intraknit zones for enhanced mobility, this layer excels in aerobic activities like running, hiking, or skiing, keeping you cool and dry during high-energy days.

　　Tech Features: A mix of merinos moisture-wicking, temperature-regulating, and odor-resistant benefits with the softness and cooling traits of TENCEL Lyocell. Seamlessly knit mesh ventilation in gender-specific zones aids dryness and comfort during high-intensity activities.

　　Designed for a body in motion, this base layer offers a supportive fit that enhances performance and training. Minimal seams reduce chafing for a distraction-free pursuit.

　　Temperature Guide: 25°F to 40°F.

　　Intraknit Active Base Layer Crew — Mens

　　(Photo/Smartwool) Shop Now Intraknit Active Base Layer Bottom — Mens

　　(Photo/Smartwool) Shop Now Classic Thermal Merino: Reliable Warmth for Everyday Cold Why it’s great: A classic choice for cozy warmth, the Thermal Base Layer offers consistent insulation for everyday winter outings, whether you’re walking the dog or exploring snowy trails.

　　Tech Features: Flatlock seams minimize chafing in this crew neck with raglan sleeves. A back body seam wraps to the front for a body-enhancing fit. The updated fit improves functionality and aesthetics for many body shapes.

　　Temperature Guide: 30°F and below.

　　Classic Thermal Merino Base Layer Crew — Womens

　　(Photo/Smartwool) Shop Now Classic Thermal Merino Base Layer Bottom — Womens

　　(Photo/Smartwool) Shop Now All-Season Base Layer: Year-Round Versatility for Milder Conditions In short: Designed for cooler temperatures that don’t require heavy insulation, the All-Season Base Layer offers breathable comfort and moisture management for transitional weather and lighter layering needs.

　　Tech Features: Crafted with lightweight merino jersey fabric, it incorporates a recycled nylon core for enhanced durability, while keeping 100% merino wool next to the skin. Flatlock seams, along with offset shoulder and side seams, reduce chafing for increased comfort. The side seams wrap to the front for a body-enhancing fit.

　　Temperature Guide: 40°F and above.

　　Classic All-Season Merino Base Layer Long Sleeve — Mens

　　(Photo/Smartwool) Shop Now Classic All-Season Merino Base Layer Bottom — Mens

　　(Photo/Smartwool) Shop Now A Base Layer for the Occasion Finding the right base layer will reward you with a balance of warmth and wicking performance for the days conditions.

　　As you can see, Smartwool makes base layers in several weights to provide warmth during winter activities. Innovations like Intraknit improve the fit and wicking performance of these base layers for high-output activities like skinning or running. More casual days like hiking or working outside tilt the balance toward a need for warmth over breathability.

　　Even if the days weather or activities change from your plans, youre still wearing merino wool and can enjoy its great range of thermoregulation.

　　(Photo/Smartwool) This post is sponsored by Smartwool. Find more wool base layers online.