The ultrafine merino wool of the men's REI Co-op Merino 185 long-sleeve half-zip base layer top is an ideal soft, breathable, odor-resistant layer for sweating on the trail—and sleeping in a tent.

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Naturally odor resistant, the ultrafine merino wool of the soft, breathable women's REI Co-op Merino 185 long-sleeve half-zip base layer top is ideal for sweating on the trail—and sleeping in a tent.

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For everything from sleeping to sweating on the trail, the ultrafine merino wool of the women's REI Co-op Merino 185 long-sleeve half-zip base layer is ideal. It's soft, breathable and odor resistant.

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Built with soft merino, the Icebreaker Merino 200 Sonebula Long-Sleeve High-Neck Thermal top regulates body temperature in all weather conditions while resisting odors. High collar adds coverage.

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Improved with a new fit and colors, the women's Smartwool Merino 250 Base Layer Crew top helps you look and feel better with perfect midweight warmth and dry comfort for your active best.

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Warm merino bottoms for the coldest months, the women's Icebreaker Merino 260 Tech High Rise base layer leggings are great for winter layering on skiing, snowshoeing or other cold-weather adventures.

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Suit them up for cold epics in the kids' Icebreaker Merino 260 Tech Long-Sleeve Half-Zip Thermal top. This midweight base layer is designed for easy layering and temperature regulation on active days.

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Layering is smart when you know the mercury will dip and rise on your hike. The Smartwool Merino base layer tee works well undercover on cool mornings or as a standalone piece in warmer temps.

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Stay dry on the trail in the soft, breathable and naturally odor-resistant REI Co-op Merino Merino Bikini Underwear for women. They're made to keep you comfy throughout the day.

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Stay dry on the trail in the soft, breathable and naturally odor-resistant REI Co-op Merino Boxer Brief Underwear for men. They're made to keep you comfy throughout the day.

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Stay dry on the trail in the soft, breathable and naturally odor-resistant REI Co-op Merino Boxers for men. They're made to keep you comfy throughout the day.

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Move with ease and layer to your heart's content with the the low-impact REI Co-op Merino Bralette, made with a sweat-wicking merino wool blend and ready for the day ahead.

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Stay dry on the trail in the soft, breathable and naturally odor-resistant REI Co-op Merino Merino Hipster Underwear for women. They're made to keep you comfy throughout the day.

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For reliable comfort at your very first layer, here's a go-to choice. Cut to fit your curves, this Smartwool Merino Lace thong breathes, wicks moisture, regulates temperature and resists odor.

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