Rigid projections that are not required to operate essential accessories are not permitted on the inside or outside of the outer shell. Fitting a Helmet An improperly fitted helmet will not do its job and may prove to be very uncomfortable when you are riding. Take the time to fit your helmet properly. Try on several helmets from different manufacturers and in various sizes. Do not purchase a used helmet.
Helmets eventually conform to the wearer's head.
Step 1 Use a cloth measuring tape to determine the circumference of your head. The circumference should be measured at approximately one inch above the eye-brows in front and at a point at the back of the head that will provide the largest possible measurement. Compare this measurement to the following conversion table. 63 Step 2 Try the helmet on and fasten the chin straps. If the helmet falls down over your head with little or no resistance, its too large.