buying a helmet is a thing that takes time, if your in a hurry or short on time, then pick another day,,, A helmet should be a good firm fit to your head & only move when your head moves,,, the other consideration is weight, wind pressure on a heavy helmet can give you a stiff neck after you start to knock up a bit of milage,, So when you try on a helmet that feels good, keep it on, walk round the shop, look at all his other gear, but keep the helmet on,, any tight or uncomfortable areas will soon let you know they're there after about 20min's, the longer you can keep it on so much the better,, it's your money, so make sure what you buy is right for you,,,,,,, expensive is not always best, in bike mag tests some of the cheaper helmets have performed better than those costing £200