Made in Finland by people who know how to stay warm when it's cold, this is the best next-to-skin layer in the world. Polypropylene is widely known as the best wicking fabric, but even with traditional polypropylene you can feel periods of damp chill when your body builds a layer of sweat or you simply get wet. But with the Airbase's big air pockets, you have nothing contacting the majority of your skin surface, while adjacent polypropylene wicks moisture, so you always feel dry. You can wear pretty much anything over the top of it and feel comfortable and dry, in any weather. And if you're out on a day that gets hotter, you simply expose the base layer and, voila, you get instant full-blown cooling. So you can literally wear this stuff right into a warm day, and regulate your temperature more easily than with any other garment. Made of polypropylene with silver ion scent control. Shirt has knit collar and cuffs. Gray.