What you need to check is the inside of the helmet, the better quality ones have adjustable /removable inserts. The cheap china ones just a solid pice of polystyrene.
Airsoft Forums UK
Jedi_Master
Jedi_Master
This shows inside of one (http://www.365airsoftshop.com/emerson-exf-bump-helmet-with-protective-gogglede-p-2802.html)
Jedi_Master
Cannot get the links to work
http://www.combatgearing.com/index.php?main_page=product_info&products_id=16794
http://www.combatgearing.com/index.php?main_page=product_info&products_id=16794