Which brings me back to the original question: make sure that your helmet doesn't only fit when it's on perfectly. I tried on a Limar Superlight the other day, which I'm sure is a fine helmet, but won't work for my head. It perched fine on top of my head when I adjusted it closely, then I loosened it just a smidgen and gave it a light knock in front, as if I'd fallen off and landed on my face, and the entire helmet slid all the way back exposing the front of my head. My Giro doesn't do this, it'll slide a little back, but not very far.