Aclima's Men's DoubleWool Longs are the warmest long underwear available from the brand. The clothing is made up of two layers of material, with an outer layer that is 100% merino wool that provides a great and snug fit. The waistband elastic is made of soft merino wool on the inside against the skin. The DoubleWool is a combination of two of Aclima's top-quality materials, WoolNet and WarmWool. WoolNet creates insulating air pockets between the two layers and transports moisture to the next layer. WarmWool insulates even more while sending moisture further away from the body. The clothing is reinforced with ribbed fabric on the inside of the knees and thighs for better durability and mobility. DoubleWool is an excellent choice as a base or middle layer, whether you're going on an expedition, sitting still while hunting, or out in harsh weather. WarmWool is made of 100% merino wool, while WoolNet is made of 80% merino wool and 20% polyamide. The wool is 20.5 microns, WarmWool is 200 g/m2, and WoolNet is 120 g/m2. Merino wool is a sustainable material that does not need to be washed as often as other materials. It is naturally resistant to odor and perfect for outdoor winter training. Wool absorbs sweat and water vapor, and insulates well even when wet. It is also certified by Öko-Tex Standard 100 and Woolmark.