Prusa Core One vibration-damping legs, Short and Very Short, with TPU bottom and core, no supports needed

These legs come in two length and bolt into the two existing 3mm threaded holes on the bottom of the corners of a Core One. 

There are two versions: short (adds about 26mm of height) and very short (add about 16mm).  Replaces or supplants the stock stick-on feet; if you have the small L's just peel them off, if you have the two long strips on the sides of the printer you can just cut them back a little.

I use interlocking between the rigid filament and the TPU, and that seems to do a good job coupling them together for vibration transmission.  the TPU goes deep up into the rigid parts to create more absorption of vibration.

I advise using PETG or better (instead of PLA) for the rigid filament, as PLA creeps.
Shore 95A TPU produced a noticeable reduction in transmission of vibration to the cabinet the printer is on; the printing is noticeably quieter.  And of course they don't come off when you slide the printer like some stock ones do.

Four of the short legs used a total of 174g of rigid filament and 59g of TPU.
Four of the very short legs used a total of 145g of rigid filament and 59g of TPU.

Note that the same TPU modifier is used for both versions of the legs.