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- SmartwoolClassic Thermal Merino Lettuce Edge Base Layer Bottoms - Women's$82.73Save 28%compared to  $115.00(1)1 reviews with an average rating of 5.0 out of 5 starsUnderwear Weight:MidweightSize Type:RegularREI OUTLET
- Deux par DeuxThermal Underwear Base Layer Set - Kids'$35.83Save 50%compared to  $72.00(0)0 reviewsUnderwear Weight:MidweightSize Type:Regular
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Related Expert Advice articles
Learn which clothes to bring backpacking in order to keep your pack light while making sure you'll have everything you need.
Your choice of underwear can have a big impact on your comfort while hiking. Learn what fabric, style, fit and features to look for.
What material is best?
Wool is moisture-wicking and odor-resistant, while synthetic fabrics are more durable and less expensive.
Match the temp to the trek
Lightweight layers are best for moderate to cool temperatures. Midweight layers are best for cold temperatures. Heavyweight layers are best for below-freezing temperatures.
Find your fit
To be able to wick sweat efficiently, your next-to-skin layer needs to actually be next to your skin. A comfortably snug fit everywhere is your goal.
Learn about clothes that can help you hike more comfortably, and get strategies for cutting the weight and bulk of clothing in your pack.
Learn the basics of layering clothing so you can stay comfortable outdoors. Find out how to use base layers, middle layers and outer layers to stay comfortable and active.
Whether you're working out, hitting the trail, or just enjoying a relaxing day, the perfect underwear is critical. We've rounded up our favorites!