It all started here: the HEATGEAR Full T. You'll never wear a non-performance T-shirt again. For extremely warm weather, Heat Gear pioneered the revolution of UA's "second skin" design which gives you the support you need without restricing your movement. The high performance line fits tight on the bodylike you are wearing nothing at all. Perfect for underneathe hot body armor. This Under Armour original will look, feel and perform unlike any other shirt you have ever worn. Featuring the UA tactical stealth logo. Available in Small - 3XL.

Sizing chart: http://www.underarmour.com/mens_size_chart.html (Cut and paste in a new screen on your web browser.)