To find your head size - Using a measuring tape, measure the circumference from the center of the forehead around the head, just above the ears. Not all manufacturer’s reference helmet sizes by name (small, medium, large, etc.) - the size names are provided here as a reference. Not all helmets from each manufacturer are available in all sizes. In addition to head circumference measurement for each size, the shape of each manufacturer’s helmet varies. Race and full ear coverage helmets fit more snug than those that do not cover the ears. Some helmets also have adjustable fit. This is just a guide - It is recommended that you try each helmet on to find the proper fit for your head.