Thermal Tech Bottom  Alpinestars Thermal Tech top and bottoms, are part of Alpinestars range of base layer underwear developed for layering purposes to provide core temperature regulation and comfort for all types of riding conditions. The Warm Tack base fabric used for both the top and bottoms is Nano treated to increase circulation of the capillaries to promote warmth. The fabric is also treated to wick away moisture and keep the body comfortable. The compression fit reduces muscle fatigue in the upper and lower body, increasing riding comfort.