Loosen the retention dial at the back of the helmet.
Position helmet on the head so that the front of the helmet is just above the rider's field of vision.
As a guideline, the front of the helmet should sit approximately two finger widths above the rider's eyes.
CAUTION: The helmet must not sit back on the head.
Tighten the retention dial until the helmet fits snugly on the rider's head.
Adjust the helmet straps so that the "Y" sits just below the rider's ear.
Adjust the chin strap so that it is snug (but not too tight) against the riders chin. As a guideline (1) the strap should push against the riders chin when the rider's mouth is fully open and (2) you should be able to just barely fit three fingers between the chin strap and the rider's chin.
Rider should shake head vigorously. The helmet should remain snug and tight on the rider's head.