So I normally wear between a size L or XL in the Assos brand for both tops and bottoms. I first order a size L since the fit description says "regular". When I first put it on it fit tight around the chest, so I decided to order an XLG, which is actually two sizes up. At first it fit fine, but I then realized it had a lot of sag around my mid torso and the neck fit rather loose. So I kept the size L. To my surprise, once you get in the riding position, the jacket does not fit tight around the chest anymore! It fits very tapered around your arms and torso with no flapping in the wind, which is one of the features I was looking for. The material performs as described; it takes the edge of the cold, chilly air and the fabric breaths better than just about everything I've worn before. It balls up to the smallest size and weight I've yet seen. So far I'm happy with it. It could be just a hair larger and longer at the waist and i would call it perfect! We will see how durable it is over time.