Providing first-layer warmth, the Saxx Roast Master Midweight Crew base layer top has a textured knit that's peached for softness, while its construction regulates airflow, insulation and moisture.

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With beautifully detailed patterning and a soft merino wool fabrication, Kari Traa Rose base layer bottoms go beyond basic and are perfect for cold-weather activities.

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Knit with a Nordic-inspired floral design, the women's Kari Traa Rose half-zip base layer top is made from insulating merino wool for next-to-skin comfort, natural odor-resistance and breathability.

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Made from lightweight fleece that's brushed on both sides, the kids' Odlo Royale half-zip mid layer has a high collar with half-length zipper so they can either seal warmth in or vent it as needed.

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Built to support you through the most gravity-defying poses, the Beyond Yoga SD Lift Your Spirits bra keeps your flow distraction-free and your styling on point when you're hitting the mat.

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Your next-to-skin layers should always be extra comfy, which is why Smartwool makes the Seamless Racerback bra. A comfortable seamless merino wool interior combines with an outer designed for support.

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No more itchy seams and stifling fabric. The Smartwool Seamless Strappy bra feels is here to help you perform comfortably with engineered knit cups for shape, lift and hold during low-impact activity.

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Crafted with high-output activities and travel in mind, the men's Patagonia Sender boxer briefs offer the moisture-wicking power and cool feel of recycled nylon blended with stretch micromesh.

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Get comfy and keep warm with the women's Kari Traa Silja long-sleeve base layer top. The soft merino wool of this colorful Scandinavian-style top will have you reaching for it all winter long.

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Whether under your hiking kit or just under jeans around town, the women's REI Co-op Silk bottoms make a great foundation as temps start dropping.

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Some wear it as a smoothing base for daily wear. Some wear it as a light and warm base layer under their gear. Either way, the women's REI Co-op Silk camisole makes a great foundation.

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The REI Silk long underwear bottoms are smooth, soft and incredibly comfortable. They'll help keep you warm on a cold day and they work great under additional layers.

base-layer-bottoms

The REI Silk long underwear bottoms for women are smooth, soft and incredibly comfortable. They'll help keep you warm on a cold day and they work great under additional layers.

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Lightweight and supple, the REI Silk crew shirt provides great warmth for its weight and offers luxurious comfort.

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