Smartwool Men's PhD Ultra Light LS Top - in stock now. FEATURES of the Smartwool Men's PhD Ultra Light LS Top Smartwool's lightest weight Merino/polyester blend helps fabric move moisture, dry quickly, and maintain its shape in high-sweat activites Thoughtfully designed raglan sleeves remove underarm and shoulder seams Flatlock seam construction designed to eliminate chafing Gender-specific body-mapped mesh panels for additional breathability and moisture management 360° Reflectivity for visibility