After trying a few on, I chose the Trek Circuit over the Giro Ionos, because it fit my head better. It feels as close to not wearing a helmet as anything I've ever worn, and the ventilation is great (even by Arizona standards). I wasn't wearing a helmet on my daily commute, because of the heat, until I bought this one. Free replacement if you crash within a year of purchase. I crashed on a charity ride the day after I bought the helmet (got the new helmet for that ride), and the replacement program was quick and painless, unlike the crash. Costs just over $100. Great value.