I got this helmet from the clearance section and the only one they had was a large. According to the sizing chart and my head measurements I should be in the upper end of the medium sizes, however this helmet fits perfect and if it were any smaller it would have been uncomfortably tight (if I could have gotten it on at all). Something to take into consideration when purchasing one for the first time as I was. Dennis Kirk was excellent on their purchase process and shipping! Helmet status was immediately changed to out of stock when I purchased it and it was shipped the next day! I had it in my hands in two business days! They even have a return UPS shipping label in the box with the product in case something doesn't work out! I call that Phenomenal customer service! This was my first dealing with Dennis Kirk, but I would definately shop here again! In fact this will be my first stop for future purchases!