It's two regular (57mm) Rubik's cubes that fit the gimmick.
It seems that there are a lot of people (you know who you are...) that pay $100.00 for this effect and then try to use a knockoff cube with different dimensions that doesn't quite work.
Incredible...spend good money on an effect and then use a junk cube from Ebay or wherever...
Regardless, it seems that PM has changed the ad copy to specifically mention Rubik's cubes...