With its moderate compression, the X Bionic Energizer 4.0 Shirt Round Neck Men meets all the needs of demanding winter athletes who want to benefit from outstanding comfort and performance-optimizing thermoregulation at the same time. Its ultra-dense knit integrates 13 highly effective technologies. Functional zones with temperature-balancing and protective effects are precisely positioned to support your performance on chilly winter days without feeling constricted. At the chest, the patented 3D Bionic Sphere System is active, enhanced by Thermo Syphon technology: A 40 CM2 sweat absorption area and complex 3D structures and Y-shaped elements maximize air exchange, cooling when you sweat and warming when you freeze, now faster and more efficiently than ever.