Love this jersey with the matching bodypaint bib shorts. It runs 1 smaller than usual castelli. I'm 6ft, 165lbs and squeeze perfectly in an XL.
Definitely for cold rides. They are a little thicker and wamer than my other tights. The zippers at the ankles make it nice and tight, but I have had issues with the zipper on the left ankle scratching up my ankle pretty bad. I just try to keep a sock between it now, but pretty annoying; hence the 3 rating.
I'm 5'11'', 170lbs and wear a M.
It has been a great base layer with a jersey over top when the temperature is 45F-55F with strong winds. Parts of the shirt are solid fabric that blocks wind while otherparts are more like a net and help keep you cool. It is better than I thought i would be. I'm 5'11', 170lbs and the M/L fits great. A new staple of my cycling wardrobe.