You can buy new pretty cheep ($100-150) and you know it doesn't have someone else's coodies living in it and the size is right.

One suggestion I will make is ask them to go out to the car with you and check how it fits in the seat. One of the old helmets I had stuck out a fair bit to the rear and with the seat in the STi coming forward at the head rest it pushed your head forward and was pretty uncomfortable.

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Stoner & Webber 2011 World Champions