The REVO X Short Sleeve Baselayer delivers next-level comfort and AERCELL™ cooling technology that lowers skin temperature by 2°C (3.6°F) and boosts energy output by up to 2%. Built with a 5x faster moisture-transport back panel and 100% friction-free ACROFUSE™ seams. Tight in the arms, looser in the body. Engineered in Switzerland.