Helmet sizing
 

OK, this sounds pretty simple to me: how are cycling helmets measured?

Given the sizes I see in ads, and taking a quick pass around my head with a tape measure, I am guessing that is what the sizes mean (for MET a large is 59-61 cm, for example).

Does anyone know for sure? If this is the method, where is the measurement taken?

Thanks...Gary

Just to add to the confusion, Gary, traditional American hat sizes use head diameter, rather than circumference.

Performance and Nashbar generally have sizing information on their websites. And they use circumference.