Love this top. 5’6”, 125#, small fits perfectly.
For reference, I'm 5'7" and 134lbs. I wanted the two piece kit mostly for training as I LOVE the one piece speedsuit. I did find the small top to be a little more snug which would be perfect for racing as it would be more aero. Ultimately I went with the medium size mostly for comfort reasons. I stay nice and cool despite the dark colors. The material is amazing. Fit is perfect. I just love the colors.