Size

There's more to fitting a helmet than just buying the one that matches your hat size or guessing at “small, medium or large.”  However, hat size is a good starting point. Measure your head at its largest circumference – usually just above your eyebrows in front, over your eyes and around in back. Try it several times so you know you've gotten the largest number. If your head size falls between the numbers on the size chart use the larger size. Most helmets are marked and sold as S, M, L or XL, so you may need to contact the manufacturer for size equivalents. Helmet sizes vary among manufacturers and model types.