Duofold by Champion Originals Mid-Weight Wool-Blend Men's Thermal Shirt KMO1, Bl 2-LAYER 6.3-OZ. FABRIC: 100% cotton inside 65% cotton/25% Merino wool/10% nylon outside 6.3-oz. fabric has two non-bulky layers. Outer layer contains Merino wool for natural insulation. Inner layer is pure cotton for softness next to your skin. Together both layers trap air to create a warm thermal barrier. Close-to-body fit allows for easy layering Details include tag-free banded crewneck and non-chafe flat-locked seams. Great on its own or as base-layer thermal underwear.