This is a replacement wheel bearing for the coal car in the O-scale Lionel Polar Express train set. It might work for some other cars as well, but it is definitely not universal. This slides into the truck from the bottom and snaps in place.
Printed in PLA with 0.4 nozzle, 0.05mm layer height, and supports (0.2mm z distance worked best). I printed on an MK3S and it worked fine.
The author marked this model as their own original creation.