[JP]

Always choose a FR (fire retardant inner liner), step away from M helmets, they are not built for Car Racing. The Nylon inner liner burn and melts in your face...not good.
A Full face helmet is probably the best buy, the open face helmets are on there way out of the rule books.

A good helmet that fits well is always worth the money. I would not choose the S, M, L, XL sisze helmets, If you instead choose the hand built helmets in 1/2" inch sizes will you propapbly get at helmet you like.
Besides that is the choice between big or narrow eye opening, Drivers in S/SS and other brake classes do prefer the big opening. AND finally, alway shut the shield when racing.

And, the SNELL 2010 standard will be available in october.