Hi Paul. I bought 8000 odd LEDs directly from a company in China. They did send me a spec sheet at the time. There is a mention of pulse width, but I don't understand it - something about "Ifp Conditions : Pulse Width < 10ms < 1/10". Please see attached.
So the shift registers are in a way an extension of the arduino board pins (so that each pin can be individually wired rather than multiplexing). I'll do some "googling" to see this setup.
Φ5 flat top green tint .pdf (356 KB)