Runs even smaller than the usual Castelli product. I would almost suggest getting 2 sizes larger. Sufficient padding that is perfect for race day.
I have owned many brands of helmets in my cycling lifetime and the Kask Vertigo gets my vote for the most elegant design, comfort and fit. If this helmet were to cost $500 I would still feel the high price is justified. I wear a large in every brand of helmet and the large in the Kask Vertigo fits just like all my other helmets.
"If you have a $10 head, go ahead and wear a $10 helmet" I am not implying that this helmet is safer than others but my old motocross coach used to tell me that. I thought it was appropriate.
Can you use a new 10 speed Dura Ace chain on a new 10 speed XTR crankset?
If you are slender(racer body), then Castelli is the brand for you. I am 6' tall and 170lbs with 31" waist and 39" chest. In Castelli I wear a size Large. I like a good tight racer fit as where my buddy of exact build prefers Castelli gear in XL but my opinion is it looks silly being slightly loose. If you have a belly really size up or buy another brand because it will show. I have almost every model of higher end Castelli jerseys and the Prima is definitely one of my top picks. Pair it up with the Body Paint 2.0 bibs and it just doesn't get any better.