Helmet manufacturers all shape their helmet differently. NEVER buy a helmet that you haven't tried on first! I use the Scorpion EXO 700 helmet. It is a oval head shaped helmet (despite what WebBikeWorld says). It has THICK padding (good for comfort, but bad in that it settles in about a size larger). I made the mistake of buying a size that fit. Due to the THICK padding it broke in to a a size larger (making it almost too loose fitting). Now the good news about Scorpion.... IF your helmet it TOO tight (or TOO loose) you can order cheap replacement helmet liners (about $28 usd). Scorpion makes 2 size helmets. One shell (small) is for size x-small to med, the large shell is for size large to xxl. So...if you have a size anywhere near cut-off, contact Scorpion at
www.scorpionusa.com and explain. They will give you the correct liner (the size diff is made up with the liner alone) to fit your head. The only time a liner can not help you is if you (like me) have a size large and need a med, or have a size med and need a large (as med-large is where the shell size changes).