Buying and getting the right size helmet can be frustrating at times, but with the right measurements and knowledge of how your helmet should fit, it should not be all that hard to accomplish.
Sizing
Proper Helmet size is a vital component to the performance of a helmet during an impact. In order for the helmet to perform properly during an impact, it must stay securely on your head.
Measuring your head is the starting point for the entire sizing procedure. Due to varying shapes, heads that are apparently the same size when measured by a tape may not necessarily fit the same size helmet.
A small measure tape or a cloth tape may be used to make your initial measurement. Alternatively, a string can be used which then can be laid against a measuring tape or ruler.
The circumference of your head should be measured at a point approximately one inch above the eyebrows in front and at a point in the back of your head that results in the largest possible measurement. Take several measurements to make sure you have the largest one.
Deleted the ebay link... (this guy is trolling various MC sites).
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