Fabric Content with the Difference of Flora Underwear; 47% Polyester 47% Viscose 6% Elastane Why should I use thermal underwear? It keeps the heat created by your body in cold winter conditions. While cotton products give off nearly 100% of the body heat, thermal clothing retains 80 percent of the heat in the body thanks to their special technology. This ensures that our body does not get cold in cold weather. While doing this, thermal clothing also has the feature of not keeping sweat on you. Therefore, the sweat that occurs while doing active sports or working does not remain in the body, but is transferred to the layer above. In cotton clothes, you feel sweat as wetness. Cotton product sticks to your body when wet and invites diseases because it does not dry quickly. Thermal products expel sweat, dry quickly and help you stay healthy.