UA Base 4.0 is our warmest yet, locking in your body's heat to deliver extreme warmth in the extreme cold; UA Scent Control Technology to keep you undetected in all pursuits; Soft, brushed grid interior traps air against your skin, managing your body's microclimate to keep you warm & comfortable; Material wicks sweat & dries really fast; 4-way stretch material moves better in every direction; 78% Polyester/22% Elasterell