Technical base layers and long underwear use synthetic materials to wick moisture and perspiration away from the body where it can evaporate. Proper base layers can make a huge difference in comfort when you're out on the mountain, so it's worth it to invest in a high quality pair like those sold at Aspen Ski and Board. Buy long underwear from Patagonia, Under Armour, Polarmax and the North Face and keep your kid warm, dry and having fun. We have a variety of base layers with varying levels of warmth like the Polarmax warm, warmer and warmest base layers. All long underwear is sold for the lowest price available.