I during a small study break I quickly made this model as a practice. It is the basic block of the Fischer Technik play system (comparable to lego but much more advanced).
I loved the system and it was part of the reason I am studying engineering now.
Unfortunately I don't have the exact measures of the diameters of the block. So they might be slightly off. I made it as close to what I had in memory as possible. I also included the catia source file if somebody wants to change the dimensions.
The video of the printing: http://www.youtube.com/watch?v=VSkScxkBQAk
Print it out multiple times and have lots of fun!