How to choose base layers
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.