Mid weight, two layernFlat seam constructednMachine WashablenMid-weight, two-layer thermals combine cotton for next-to-skin softness with a Merino wool blend for natural insulation and thermal protection to keep warm in very cold weather. Flat seam constructed for smooth, close to skin fit. Inner layer 100% cotton, outer layer 65% cotton, 25% merino wool and 10% nylon.