The endura mtr race socks are an extra warm sock built using thermolitereg fabrics thermolitereg uses hollow core fibre technology to create an insulating layer of warm air keeping your feet nice and toasty even in the coldest temperatures the socks also have variable engineered zones for optimal breathability lycra fabrics ensure a skin tight wear offering optimal stretch with a support zone at the arch of your foot for ultimate comfort the endura socks also feature durable nylon heel a