Specialized tests to the old B90 standard, which is almost identical to the CPSC standard in impacts and drops. The test regime is much more exacting, however: with CPSC, you take some helmets to your choice of test lab, they test 'em, and you slap the stickers inside - it's practically an honor system. With Snell, they do the tests and as a follow up, snag the occasional random helmet from a retail outlet and retest.