Originally Posted by martys
I picked up a C3 over the weekend at my local dealer. (sorry Anthony, I like helping out my local dealers whenever I can) I'm a solid medium in the Arai's but what really matters is the actual size of your head. I'm 57.5mm. Arai sizes their mediums at 57-58mm, but Schuberth sizes their medium 56-57mm. My C3 is a little snug, but I'm expecting it to pack down after a few days of riding to be just right. According to Schuberth's sizing chart, their large is 58-59 which I know is too big for me. The medium and large use the same size shell so if the medium doesn't pack down enough for me I'll buy a thinner liner and swap them out.
bottom line is measure your head and buy the right size by your head's circumference.
Which Arai are you wearing that you're a Med. in?