No clue in centimeter but i wear a size 8 in fitted hats and thats the biggest they get (new era hats) and this helmet has some room to spare you shouldn't be concerned with size it should fit you if it fits me
This helmet is adjustable, I am sure it would work fine..I have wore mine quite a few times now and it is very comfortable. The only thing that I have added is rear view mirror...a small mirror that mounts to the helmet and allows you to see behind you...I wasn't to sure about how effective the mirror would be, but it has been a nice addition. Just my $0.02 Ken
I have a large head: and in the past I have had problems getting low-end helmets to fit. I was easily able to adjust this helmet. This helmet (the Schwinn Thrasher) is only for bottom-fishers. The decorative plastic veneer, in the case of my helmet, "shrunk" and has now practically fallen off: low-grade thermoplastics. But I am generally unconcerned about decorative aspects of sports-gear - so I continue to use the helmet. My sense is that the suspension system is well-engineered. I am not unhappy with this helmet: and the price is right.