>>9843691On bricklink they are under the "Arm" category of parts.
They were included on sets from the 80's (in light grey) to the early 2000's (in yellow and such).
They were abandoned just like the plate based finger hinges because they lose friction easily over time, and the transparent ones have a tendency to crack under stress.
They are very cool though - I enjoy them way more than click hinges, but they are certainly more fragile.
