There is not a modular helmet that I know of that meets the SNELL Safety spec for helmets
The Difference Between SNELL & DOT Ratings
Snell Standards
The Snell rating is a more stringent rating, and is completely voluntary, meaning that helmet manufacturers can choose whether or not they wish to meet Snell's advanced safety guidelines. Snell standards are set to levels that only the best, most protective headgear will meet. Moreover, Snell certification is more than simply high "standards", it is based on actual testing of actual helmets.
DOT Standards
The DOT rating simply indicates that a manufacturer believes that its helmet meets the basic DOT standards, without any actual testing on the helmets themselves. In that sense, DOT ratings are fairly easy to come by, and virtually anybody can make and sell a helmet with a DOT sticker.
Fortunately, DOT personnel periodically buys helmets and sends them to independent labs for testing to assure that they actually do meet the standard. The results are posted on the NHTSA website in a pass/fail form. You might be surprised to learn that more than half of all helmets recently tested with the DOT sticker on them actually failed DOT's lab tests. Check it out!
Keep in mind, if you purchase a "novelty" helmet without either of these safety ratings (Snell or DOT), you may look the coolest, however the degree of protection you'll receive in the event of a crash will be minimal. How cool will you look then?
If They're The "Best", Why Aren't All Helmets Snell Certified?
Some helmet manufacturers do not believe that they need such certification to demonstrate that theirs is quality protective headgear.
Some are content with meeting the minimum requirements for helmet safety.
Some helmet manufacturers try to meet Snell guidelines and just can't make the grade.
Some helmet makers could care less about the consequences of making an inferior safety product. Instead, they opt for the best "look", or the cheapest price.
Go to
http://www.smf.org/ "Snell Foundation" to learn more about Helmet safety