What is the maximum speed a red laser can read a dual layer DVD?

Just curious… I read somewhere that 12x was the maximum a red laser could read dual layer DVD ROM…

Just need confirmation if possible.

More would be useless. Imagine what it would mean for the drive, the media AND the hardware error-correction!

My Benq 1620 starts at about 6X and hits about 16X to layer break then starts back down.( On most pressed DVDs)