Make sure you stay warm when you train on colder days wearing the Under Armour Womenâs Tactical ColdGear Infrared Base Mock Long Sleeve Shirt. This top has a ColdGear Infrared lining that traps in your natural heat to keep you feeling toasty warm, and the moisture-wicking technology helps you stay cool and dry. Under Armour Womenâs Tactical ColdGear Infrared Base Mock Long Sleeve Shirt Black/Black, X-Small - Women's Athletic Performance Tops