. Get Price Send E-mail The British Mark I Brodie & the U.S. P00 know the difference This ,difference, along is enough identify the origin of the ,helmet,. Both the British and American ,helmet,'s have marking stamped into the steel on the underside of the ,helmet,'s skirt. In the case of the British Mark I there is typically a letter followed by a slash followed by another letter. Get Price Send E-mail Should I get a Medium helmet or a Large.. apparently I am ... 00/0/0000, · The proper fit in a ,helmet, can be the ,difference between, enjoyable riding and unenjoyable. Too tight, your head will hurt. Too loose and you will not feel stable at speed. Don't get set on one brand, try as many as you can, get the right fit and the full face ,helmet, that feels best for you. Get Price Send E-mail 