Like all my gear from Castelli the fit on the Perfetto ROS vest is, well, perfect. I guess that why they name it perfetto. The materials is very stretchy and aero. I also like to high collar to keep out the wind. The vest fills a particular need when the weather, in late winter and early spring, is so unpredictable. Where I live in the mountains of East Tennessee, my early spring rides usually starts out in the high 30s, maybe 40 at most. By the middle of the ride it will be in the 50s. The vest provides just enough warmth and when you get hot the Goretex lining let your heat out without the sweat. I usually takes it off mid ride. The vest rolls up into almost nothing. I have used it in light rain and it protects my core from the elements. The two pockets are nice and big. The pump sleeve is pretty useless-who wants to carry a pump in your back pocket when it can impale you in a crash!
This vest is perfect for cool days or early morning rides when the full sleeve jacket is overkill. Gortex fabric. It keeps me warm without overheating and is easy to roll up and stuff into my jersey pocket as the day warms. Fits me well, I'm 5'10 145,bs. . Highly visible.
Vest is definitely a race cut. Much smaller than my Castelli Puro jersey in same size. Short in torso. No way it would fit over my jersey. Very much doubt it would fit it I sized up. Other than fit, it was a very nice vest.