Under Armour Ultimate Short Boys Fit: Loose--Generous cut for ultimate comfort and ease of layering. Performance Technology: Under Armour HeatGear --For when it's hot. HeatGear technology wicks perspiration off your skin, rather than absorbing it. It's engineered with UA's Moisture Transport System to deliver core temperature regulation and maximum breathability. Ventilation--Mesh or breathable fabric inserts in high heat zones allow sweat to evaporate and cool air to circulate. Fabric Content: 100% polyester