Bell Pro 3 Helmet, 7 3/4", Motocross, BMX Bike Racing.  I don't actually see a size inside or outside of this helmet.  I based this on the size of my head.  Normally I am a 7 1/2" head.  This helmet still has plenty of room for my head.  So I am saying it is 7 3/4".  Take a look at the multiple pictures, its not perfect.  Inside is well worn, not through, but as you can see it has been worn.  Normal nicks and minimal missing paint on the outside.  Take a look at the pictures and make your own determination if this will work for you.  Bookmark my store, I add new and interesting items every week.