Tuftes Frost baselayer is warm, light and incredibly soft woolen underwear for women, men and children. The garments are made from 100% superfine, 18.5 micron merino wool. Super soft wool in other words! The natural and wonderful properties of wool will keep you warm even if you get wet or sweaty. Frost is a thin innermost layer that is used next to the skin. Dress in layers with Frost on the inside for good warmth.