Under Armour ArmourVent Run Short - Men's Body: 88% Polyester/12% Elastane, Back Yoke: 100% Polyester, Lining: 100% Polyester ArmourVent Mesh Technology delivers true breathability in a light, stretchy, durable, fast-drying fabric It keeps your body cool, giving you the boost you need to keep working hard Internal mesh liner helps moisture escape and adds breathability Graphics and logos provide 360&deg; reflectivity for safer low-light runs Interior waist key pocket