Not sure about your helmet size? Get an "S1 Helmet Co. Fit Kit" and eliminate the guessing.

You'll get all 7 different thickness of sizing liners so you can fit your S1 Helmet perfectly today and if your head grows in the future.  

Size: XSmall- XXX Large included in fit kit.

FIT KIT sizes all S1 Lifer Series shells!

(S1 Mini Lifer Helmets 18.5" - 20.5")

(S1 Lifer Helmets 21" - 23.5")

(S1 Mega Lifer Helmet 24" - 25.5")