ZOOT SPORTS Men's Ultra Run Icefil Sleeveless Tee 100% Polyester Tri Cycle Fleece Imported Icefil combines Xylitol and thermal radiation nano technology, reducing skin temperature up to 5.4F/3C; Chamois: 250g Icefil mesh back for enhanced ventilation and cooling Flatlock stitch construction ensures next-to-skin comfort and minimizes chafing