A helmet should NOT fit properly when first purchased. It should be too tight. When you KNOW what helmet fits you correctly it is no problem to buy online. In my case, Arai long oval size small. Every time. It may be actually harder to buy a helmet 'in person' as you go with what feels right. My first helmet was a very nice fitting Shoei medium. After a month it was so loose that I could not race with it... Again, once you know what actually fits? Go buy it!