Our Lightweight Mid-Layer Thermal Underwear Bottoms are the perfect winter underwear for when you need to dress for the cold. Whether you re outdoors in icy temperatures or dealing with industrial freezer machines, these cold-weather underpants give you 4°F to 8°F more warmth. Our thermal tights are made from a 92% polyester and 8% spandex fabric that features 160 g of 4-way stretch to keep you warm and let you move on the job.