The unspoken rule of buying a helmet.
1/ Get your haircut just before you buy a helmet. Especially if you tend to take off lots.
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People have mentioned on here about the lining compressing and in my experience some helmets go through more compression than others. I tend to check the lining now and take an educated guess at how much it will compress. You can generally feel the difference in lining from helmet to helmet.
I'm looking forward to the day when they scan your head then produce a lining to insert in the shell for the best fit.
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