UA Seamless is a soft knit with engineered mesh ventilation, mapped to the places you need it most.Nearly sew-free construction to eliminate chafing.Where we started? It all started with an idea to build a superior T-shirt.The technology behind Under Armours diverse product assortment for men, women and youth is complex, but the program for reaping the benefits is simple: wear HeatGear when its hot, ColdGear when its cold, and AllSeasonGear between the extremes..Under Armour.