Currently our Kickstart helmet comes in one size only -- and it should fit most heads from 54-61cm, and up to 62cm. (Approx. 21.3 - 24 inches, up to 24.4 in.)
It's a simple task to measure your head size. You can check out the video below:
If you have a relatively wider head, we suggest you to try it at a store before you buy it if possible.
If you purchase from our website (lumoshelmet.co) we have a returns policy where you can get a full refund within 30 days. Just keep your packaging and note that you'll have to pay for return shipping.