From SmartWool, this T-shirt features: Slim fit that is intended to follow the contours of the body Solid tone Crew neckline Long sleeves Intraknit™ technology: insulation, ariculation, and ventilation are seamlessly integrated to help with movement and comfort during high-intensity activities Merino Sport yarn combines the power of Merino with polyester Seamlessly knit mesh ventilation 3-D mapping results in near custom fit and freedom of movement Pullover construction Merino wool/polyester/elastane Machine wash/tumble dry Imported.