This cap does breath pretty well on hot days to be sure, but it's not quite as lightweight as some competitors' caps. I really want to like this cap but the brim on it is just huge, really huge, it has to be flipped up, because if it's down you'll strain your neck seeing past it.
Great cap for keeping bugs out of your head during rides. Also provides a bit of warmth on chilly days, but mesh design prevents you from overheating on warm days. Castelli logo is more substantial, won't wash off after a couple of launderings like the previous design