UNDER ARMOUR Long Sleeve Innerwear L size Worn only twice This is golf wear featuring Under Armour's ISO-CHILL technology. ISO-CHILL is an Under Armour technology developed to free athletes from the heat and keep their bodies cool. This technology uses a special nylon fiber with high thermal conductivity, which feels cool to the touch and maintains that coolness. Titanium oxide blended into the fabric absorbs ultraviolet rays and quickly dissipates heat, allowing you to stay comfortable even in extreme heat.