I ride the smaller diameter pegs (DOM's) for a weird reason. I found that when I rode bigger (38mm) I would get bad acchilles tendonitits. When I switched to the DOM pegs it doesn't happen nearly as often.
KHE Killah was correct when saying a standard socket doesnt fit inside too nicely. However, the Odyysey travel tool socket fits perfectly. I can also see why he was saying that it hurt his feet. Since the ends aren't super rounded off pivoting is a bit painful there. However, I 3D printed some end caps that really helps me there.