Built for mutton busting, this youth-sized helmet fits a 19" to 21.2" head circumference. Sizing is set by the manufacturer and isn't a guaranteed fit — if this one runs small, the RM 50 comes in a smaller size, and the RM 3DS Youth Helmet is a higher-end option if you want to step up.
To measure, wrap a soft tape or string around the widest part of the forehead.
