The Smartwool Classic Merino Blend Base Layer Bottoms blend Merino wool with recycled COOLMAX polyester, so temperature regulation, moisture-wicking, and odor resistance all work together through a full day of snow play. Flatlock seams sit flat against the skin instead of rubbing during the constant climbing, falling, and getting back up that comes with a kid actually using the gear, keeping the fabric comfortable rather than irritating. What Our Gearhead® Experts Are Saying:"My kid wore these two days in a row on a ski trip without a single complaint about chafing or smell, which is the real test for base layers in our house. I stopped worrying about packing a second pair."