I was looking for a spaghetti strap cycling shirt and came across this, which I love, unfortunately it runs small. By small I mean it barely covers my whole back, so if I rode with it, it would ride up. Im a size small in tops, 57 in height, so you can take that for what its worth. I called up Castelli and they said that the difference in the small to medium size as far as the length of the fabric in the back goes, is about 1". http://shoespim.com/48179