There are plenty of places in the world where you can survive most of the winter with a long-sleeve base layer and jersey. However, if you try this and choose the wrong base layer, you'll find yourself pedaling back home toward the warm fireplace before you even break a sweat. That's why we recommend the Giordana Heavyweight Carbon Base Layer for winter riding -- it features precise fit, Italian design, and the ability to keep you warm and dry. To achieve this, Giordana constructed its Heavyweight Carbon Base Layer from Dryarn fabric, a relatively new kind of polypropylene fiber. Basically, it was designed with a winter-weight denier that's been knit into a tubular construction. The tubular composition of the knit creates a varied density over the form of the base layer. You'll find that Giordana designed the fabric to be thicker over your chest, but thinner on your stomach; and thicker on the front of sleeves, while getting thinner around back. This not only provides comfort while riding, but the next-to-skin fit means that the fabric is more effective in keeping you warm. Dryarn also provides moisture management in the base layer. As we all know, the warmer that you get, the more that you sweat. But, the question begs to be asked, where does all of the moisture go' If you are out and about in cotton, the answer is 'nowhere.' However, with the second-skin tubular Dryarn knit, moisture is rapidly transported away from the body. In fact, Dryarn's wicking capabilities are so immense that the base layer doesn't need a heavier weight in order to keep you warm. So, the minimal fabric weight promotes a greater ability to breathe, while actually keeping you warmer than most winter-weight fabrics.