Men's Midweight Thermal Base Layer Shirt. Cut the morning chill with this men's thermal shirt. This base layer top was designed to keep you warm and comfortable in any time of year. It's made of sweat-wicking fabric that's cut to give your arms a full range of motion and fight odors. Perfect for layering when you need extra protection from those cold weather days. 6-ounce, 100% Polyester Waffle-Knit. Midweight, Force(R) Base Layer. Built with Force FastDry(R) technology to wick sweat and dry fast. Built to move with Rugged Flex(R) stretch technology. Fights Odors. Smooth Flatlock seams and tagless label for comfort. Concealed thumb loop.