Cooling TechnologyBy using hydrophilic and hydrophobic yarns, this base layer holds a bit of moisture next to your body while allowing free airflow through the fabric, thanks to the special open knit. You get evaporative cooling directly on your skin. We recommend using this with our coolest jerseys, like the Climber\'s or Superleggera, though it will work under any breathable jersey.Key Features: Base layer to cool you on hot days, Polartec® Delta fabric features regulated drying so that the evaporative effect cools your core, Sleeveless design with minimalist construction, Sublimated overprint, 25°-35°C / 68°-95°F, Weight:84 g.