This heavy-warmth thermal top includes our Timberland PRO® FLEX technology maximum mobility features so you can bend, reach, and stretch without restriction, fabric that offers warmth without bulk, and flat-lock seams designed to not bind when worn under your favorite work shirts. Our WickWork™ technology, in combination with lighter-warmth side panels and arms, provides maximum breathability, comfort, moisture wicking, and odor resistance helping you stay dry and comfortable during active work days. We even added convenient thumb holes to keep your sleeves in place when layering.