Helmet Attachments and Straps
The tried-and-true "D-ring" attachment system is widely used, very reliable and is used on every racing helmet that we are aware of. Other "quick release" systems have been developed, but like trying to build a better mousetrap, none have improved on this basic attachment system, and most are more complicated, failure prone, and fussy to operate. Our advice is to stick with the D-ring system.
A D-ring is infinitely adjustable and there are no springs to wear out or plastic and metal latches to break. All of the quick release mechanisms we've tried make it very hard to adjust the tightness of the helmet straps.
Accessory quick release latches that are user installed should also be avoided, because they can add too much length to the helmet's strap, making it difficult to adjust correctly. Our opinion is that quick release latches are a solution in search of a problem.
One thing to look for is a button or Velcro attachment for the extra piece of chin strap that's usually left dangling after the helmet is secured. Sometimes, this extra piece can be tucked up under the attached chin strap, but it's usually more comfortable to have a method of securing the end of the strap. Make sure you know how your system works and that it fits correctly before purchasing the helmet.
Source:
http://www.webbikeworld.com/motorcyc...helmet-faq.htm