I am 5'6" and weight 138 lbs. I bought a small and it fits perfectly! Sleeve lengths are wonderful, SO SOFT and just couldn't get over the overall quality. I am very impressed and will be buying more from this brand. I'm glad the buckles on the shoulders are metal rather than plastic, because it looks like better quality that way.I hope giving my dimensions helps another because I know when I was going to buy this I was torn between the small and medium because I typically buy in medium. Glad I got the small, medium would have fit baggier and I wasn't looking for that.