Great fit & function
I got this singlet for the cool morning rides (60-70 deg), but I've continued to wear it in temps up to the low-80s. Gore's sizing chart worked perfectly for me. I'm 6'0", 183 lb. In most brands I'm a Medium, but in Castelli and Gore I'm a Large. The fit of the Large is perfect for me: snug without grabbing anywhere. It's so light that I don't even notice it once I'm on the bike.