Hi Lee, Bike helmet's come in head sizes ie. head circumference in centermeters. We bought the smallest size they do which I beleive is 48-54cm. It was a little big for our son but the way I looked at it was that it was better than no helmet. They do come with the removable foam padding which we did use that did make it fit better. We got the helmet from Argos. Hope this helps. Tanya.