H&N restraint with SFI 38.1 cert required as of June 2, 2008
Specification 38.1 - Head and Neck Restraint Systems
Hubbard-Downing HANS Device
Leatt Brace Moto-R Sport Device
LFT Technologies R3 Device
Safety Solutions Hutch-II Device
Safety Solutions Hutchens Hybrid Device
Safety Solutions Hybrid X Device
Not looking to start a debate on which ones better or why some devices aren't included - just being the messenger.
As an FYI (no affiliations, etc) - HANS apparently has a new model that just came out in the last week or so that is around $700 vs. the $900 regular models. Main difference is that the new model is a pound or so heavier and carries an SFI, but not FIA certification. So, to save $200, you're giving up your opportunity to use it in an F1 car.