The Salomon PRIMO WARM SEAMLESS TEE features a 3D fabric to provide thermal protection, breathability, comfort, and enhances the effect of thermal garments. The 37.5 technology maintains optimal relative humidity - your body maintains ideal core temperature and is able to give better, longer performance. Fabrics equipped with this technology dry up to 5x faster than other materials. The technology uses natural materials, so your skin won’t get irritated by aggressive chemical substances. The active 37.5 particles are permanently embedded in the yarn, they don't wash out or deteriorate.