Improved Replacement Feet for Royal Portable Typewriter (set of 4)

Description

Royal Portable Typewriters are really old (mine were made in 1933/1934), and originally had rubber feet that by now has the properties of chewing gum under a desk. These are replacement and much improved feet using modern techniques and materials, I think looks and functions better than the original rubber ever could have, and will hopefully last a lot longer!
I am not sure which variants of typewriter this will fit. I have tried it on two specific machines:
1) Red Royal Portable with serial number OT 349671 (1933)
2) Black Royal Portable with serial number O 397970 (1934)
You can look closely at the photos, and see if it seems to match your machine. The dimensions are 26mm x 28mm at the base, and 10mm high. The hole is offset, and the same part fits all four feet (on mine) even though the front and back use different mechanisms. In the front, an assembly removes with 3 screws, while in the back you just install the feet directly. In the end, it's the same, they use a painted black cover that is loose. To install, you put that piece on first and make sure the tab fits into the slot (it's obvious)--I used some tape to try to secure this to avoid scratching it while struggling to get the foot on. Next, push, pull, screw, pry--whatever works, to get the foot over the metal post. It's annoying, but you get the hang of it by the 3rd foot. Perhaps a little synthetic oil would assist, but I didn't use that, I carefully iterated the dimensions to achieve a balance on installability versus tight fit. So, it needs to be difficult to put on, so it stays on and in place.
I have a lot of typewriters, but have yet to replace most of the feet. These feet may fit other models of typewriter, I will update this summary when I learn more. If you can add something about general compatible among different Royal machines, please send me a message, thanks!
I designed these to be nearly an identical replacement, but with the advantages of modern technology we can engineer materials that were previously impossible. I printed with NinjaFlex Black TPU (https://ninjatek.com/ninjaflex/), which is nearly indestructible
(but a knife or scissors will cut it, just like rubber!)
, flexible, and pretty gripping on most surfaces. I printed these at 50% infill (with a flexible gyroid fill structure) for a balance between good friction on the table, tight fit on the machine, and ability to actually install them. These look and function very much like the original, but should last much longer and be far more durable. Some people may prefer the original dull rubber look, but I actually think these are a superior look to rubber, and the glossy finish better matches (if black) or accents the rest of the machine.
I designed these for my own typewriter as shown, and this is an experiment to see if it's worth my time to make some more for the community. If you have access to a 3D printer, I have shared this design online here, feel free to print your own: https://www.thingiverse.com/thing:4843037
PS: Ebay's volume discount display is a bit confusing, each purchase is a SET OF FOUR feet, so picking "1" is one set of 4; "2" is 2 sets of 4 (8), etc.