Since the rubber rings of my generic steel doorstoppers are old and brittle. One of those just broke off, i designed a replacement to repair it.

In the process i took the chance to model the entire thing including the rubber foot because this also does not look that good anymore - since it is easy to model, i did the whole thing, so it can be printed/machined if someone wishes to

The model is fully parametric (Fusion 360 file is included)

Printing

i printed the ring and foot with TPU Shore 95A from Geeetech (Affiliate Link) - printed with 3 perimeters and 25 % gyroid-infill it behaves almost the same like the old solid EPDM rubber

be aware that i only used this to replace the ring and the foot part so far and not have tried printing the core - if you print the core, i'd suggest printing it upright and pausing it higher before the curve starts, then fill it with sand or steel balls and resume the print