1storm motorcycle bike full face helmet booster iron red 1storm <b>helmet size chart</b> <br> <br> xs 53-54 cm 20.9/21.3 inch <br> s 55-56 cm 21.7/22.0 inch <br> m 57-58 cm 22.4/22.8 inch <br> l 59-60 cm 23.2/23.4 inch <br> xl 61-62 cm 23.8/24.1 inch <br> xxl 63-64 cm 24.4/24.8 inch <br> <b>helmet size tips</b> <br> <br>(1)wrap a measuring tape around your head about a half-inch above eyebrows <br>(2)take measurement two to three times to pick the largest one.