I love this Izumi cycling jacket. It's really easy to wear or carry around and very eye-catching on the go. I like the slim fit. I live in Sun Cal and the weather here really isn't as cold as other parts of the US so I don't need to wear a lot of layers of underwear. I'm 6ft 175lbs and ordered a medium size and am very happy with the fit. If you need to wear more than two layers of underwear, you should choose one size larger.