sokitset

The Arai Quantum is designed for round shaped melons. The Arai Signet is shaped more for an oval head.

I've found the Shoei products to be more oval oriented. AGV more round.

Still, don't buy unless you know it will fit. Nothing discourages the use of a helmet more than one that isn't comfortable...well, that is nothing except for owning a Harley.

Mocky

yup.. if you're really looking to go the internet route, at least try on the helmet at a local shop before you go online. i went to the local shop, tried on an arai helmet..didn't fit well, so i went with the shoei. also ended up getting it cheaper locally than online.