8 cubes in a loop with a solid plate down the middle of each cube. Of all of my cube loops, this is the hardest to turn. It's big enough to go over some fingers, but it often requires some fiddling to make the turn.

For the loosest, simplest version, try the basic cube loop. For a version that is slightly less loose, making for a cleaner turn, but still has space in the middle try the one with bars. The best turning is the thick one, but it has very little space in the middle.  The most impressive is cube in cube which is also a bit larger.