The inner layer is a blend of 50% cotton and 50% polyester for absorbency and softness next to the skin. The outer layer is a blend of 50% merino wool and 50% polyester that offers you warmth and strength. The space between layers insulates, trapping warm air from your body. The combination gives you one of the warmest garments you can put on next to your skin. These long johns are treated with an anti-microbial for added performance and feature a full roomy seat and a plush back signature elastic waistband for comfort.