The Energy Accumulator 4.0 Shirt Round Neck Men by X-Bionic is made for competitive sports and supports you with the latest technologies to strengthen your performance and endurance in all climatic conditions. This great high-tech functional underwear for winter athletes integrates a variety of thermoregulatory and protective functional zones: The patented 3D Bionic Sphere System is active at the chest and back, reinforced by ThermoSyphon technology. Complex 3D structures and Y-shaped elements maximize air exchange, cooling when you sweat and warming when you're cold - now even faster and more efficiently than ever. Retina ultra-high definition quality.