Bought myself two of each of these items...
It's kind of sad how excited I was when I found these on Amazon. I need to replace a few of my originals because they didn't survive the shipping for summer camp.
They're great for demonstrating that crystals with more empty space make for less workable metals. See, the top ones (the rainbow ones) have individual ice cube trays that are close together, little space between them. The trays slide back and forth past each other easily when they're turned so the ridges of one tray are against the ridges of the other tray.
The other ones (the white ones) have more empty space between them, bigger gaps. When you show the wider-spaced trays trying to slide back and forth past each other, the individual trays get stuck because they dip down into those gaps of the other tray.
More empty space = less workable metals