Unlike many windproof or 3 season bike jerses/jackets, this is very thin. This makes it by far the most useful and versatile jersey/jacket around.In colder weather, add a thick baselayer/thermal jersey, and windproof armwarmers and you are set for some fairly cold weather.At the same time, there are many rides where it is only the wind that is making you cold, whether blowing or from riding.This completely blocks the wind in the front, without adding any warmth. This way, once you are out of the wind, or slow down, you don’t overheat like you do with a heavier, garment. It also means you can wear a warmer layer underneath, so if you need to unzip, you don’t go from boiling to freezing.The other key part is the thin, and water repellant, fabric on the back. Too many windproof jerseys are way to warm in the back. Bike jerseys/jackets need to be warmer in the front than in the back, regardless of the absolute amount of warmth the provide. Keeping the back thin matches well with the front, so you can add warmer layers underneath if needed, without your back getting to hot.The sizing on this women’s one runs slightly large, quite unusual compared to their mens line.Saying that, it is a performance road bike fit, so when I say that, I mean it in terms of trying to get a very snug, no flapping fit.If that is what you are after, I would not size up from the sizing chart. The length is quite long too, so if you are shorter, it will be too long in the front if you upsize.The tightest part, and the only reason I chose M instead of S, was sleeve tightness.