Size Chart for the HCI-75 Carbon Fiber Sportbike Helmet DOT
Please use a cloth tape to take your measurement. It is better to have a helper do the measuring in order to get a more accurate measurement.
The circumference of the head should be measured at a point approximately one inch above the eyebrows, or at whatever point gives the largest possible measurement.
If you find that your measurement falls between two sizes, choose the smaller size.