Not sure about your helmet size? Get an "S1 Helmet Co. Fit Kit" and eliminate the guessing.
You'll get 7 different thickness of sizing liners so you can fit your S1 Helmet perfectly today; and if your head grows in the near future!
Size: X Small- XXX Large included in fit kit.
The Fit Kit also includes a 2mm top pad to lower the helmet toward, and a 6mm top pad to raise the helmet from, the ears.
FIT KIT sizes all S1 Lifer Series shells!
(S1 Mini Lifer Helmets 19" - 20.5")
(S1 Lifer Helmets 21" - 23.5")
(S1 Mega Lifer Helmet 24" - 25.5")