1. MEASURE YOUR HEAD. Determine the circumference of the widest part of your head by using a flexible tape measure.
Generally, the widest part of a person's head is the area 2.5 cm (1") above the eyes and ears.
However, we suggest measuring at a few points both above and below that line to determine the greatest measurement before referring to our size tables.
We also suggest testing the fit of a helmet one size smaller and one size larger then what the chart recommends.
No helmet can provide protection if it's too uncomfortable to wear.
If you would like further detailed instructions on how to determine your correct size please look at our AFX Helmet Fitting Guide.
Comment: This is a great helmet. Very light and comfortable. Need to order using the parameters on the CM guide. I was right on the cusp for sizing so took the safe bet and went up one size. My thoughts process was that I could alsways use the room for ear buds/phones on long trips.
There really are seven vents so if you do size up, the air will get in there and create lift pulling on your head. I really do love this helmet and would encourage anyone to buy it. I still don't understand how you guys get to my door in 2 days.