Manufacturer's Sizing Advice

Here are links to information about fit.  A couple sites list a size chart and fit advice while others have just fit advice. 

Klim (shown on each product page)

Nolan (no sizing advice on Nolan's site)

Scorpion

Shoei (shown on each product page)

Speed and Strength

Vemar (no sizing advice on Vemar site)

Z1R (sizing advice listed on some product pages)

AGV

AFX

Arai (no sizing advice on Arai's website)

Bell Helmets

Biltwell (shown on each product page)

Fly Racing (no sizing advice on Fly Racing’s site)

HJC

Icon  (shown on each product page)