Features special cooling fibers, reacts with sweat, helps to lower the temperature of arms up to 6 degrees. Spraying water on the arm sleeves gives you a dramatic instant cooling effect. Proved to block 99.8 percent of damaging UV rays in laboratory tests, the polyester base is more effective than typical nylon at blocking UV rays, maximally prevents sunburn and long-term skin damage. The arm sleeves wicks moisture when dry to absorb sweat from the body, and the special designed mesh at the back offers added breathable ventilation, create an evaporative cooling effect.