How do you call this kind of structure on the outside of track?

drift92

50RPM
Original poster
Jun 9, 2011
63
75
Could be a dumb question to ask, I'm trying to find more reference images of this structure in different shape for my friends' project. But both of us have no idea how this kind of things is called, even in our own language... :whistling::whistling:
If you have some time, please let me know how you call it x)