The Mortirolo Jacket has been designed to be a warm, cozy jacket on cool days while preventing overheating and moisture buildup inside the jacket. Choose this jacket for riding in cool but not frigid temperatures, or for high-intensity rides or if you tend to sweat a lot. This jacket excels in a wide range of conditions as long as it's not bitterly cold or raining. It's the combination of the right fabrics and construction that make it work so well. You get coldest on the upper chest and arms, so we use our GORE-TEX INFINIUM™ WINDSTOPPER® X-Fast three-layer fabric with a luxurious fleece inside for extra warmth. The lower part of the front is in our mid-weight GORE-TEX INFINIUM™ WINDSTOPPER® fabric with a lightly brushed inner face. Both of these fabrics provide 100% wind protection, excellent splash protection, and best-in-class breathability. The back is in our brushed fleece 100% polyester Warmer fabric with superior wicking. It's not windproof, so it lets a lot of moisture escape. You stay drier and therefore warmer and more comfortable. The jacket has a neutral fit. It's not too racy, so there's room for an extra layer underneath, but it's certainly not going to flap in the wind.