I recall it being ~17Hz. I saw a story where asian anime shown during flights were making people throw up due to constant flashing during the movie. 2mil candlepower light works great though.
It appears that most of those universal projector fogs are just xenon bullshit, which is not real High Intensity Discharge. No ballast, no HID. Stuff like 70 watt KC's are real, but all the shit is usually integrated into the round light, and no care given to shield the beam to on-coming traffic. You can fuck around with retrofitting a CDM bulb into a CDM projector housing, but the truth is the only effective way (for light output and blinding/fuzz-avoidance) is to use real projectors & HID's fitted into a gutted stock housing.