It's a waffle top, you already know what it does. I PERSONALLY would order a size bigger than normal if you don't want it to be super tight. 
Gen III Level II Underwear Top are part of ECWCS (Extended Cold Weather Clothing System) which provides extra warmth in cold climates. The highly breathable, moisture wicking polyester and spandex material is designed to protect from the harshest elements. The mid-weight underwear tops feature a zip up collar, long backtail, and thumbholes in the sleeves. The grid fleece fabric is anti-odor and anti-microbial.