This is an improved replacement/upgrade kit for the aged rubber parts on ~1960 era Erika 10, Aztec 700, and Optima Super typewriters. Using better modern materials, each set ordered includes four replacement typewriter feet and four replacement case feet. Please contact me with any compatibility questions, you can send me photos and measurements if you are not sure. I have two Optima Super machines, serials #1976251 and #1968880, which I think were made in 1962. They have identical cases, and use identical case and typewriter feet, from which I designed these replacements. From what I've read, and from looking at lots of photos on TWDB, I am pretty confident that these feet will fit Aztec 700, Erika 10, and Optima Super typewriters, which I believe are all the same machine. It *appears* that Optima Humber 77 (this might be another Erika 10 rebadge), 88, and 99 machines have similar feet, but we had better measure to be sure if you have one. The case foot has a 20mm diameter (6mm high), and the typewriter foot has widest bottom dimensions 20.69mm x 46.04mm and 10.25mm high. 

If you own this machine you already know this--German engineering at its finest!. I have nearly 100 machines and these are in the top 5 for sure (competing with my Olympia, Alpina, and Facit machines for the top spot). These amazing machines typically still work great today with little degradation, except the original rubber parts are long reduced to mush or bricks, variously. Part of my hobby is designing 3D printed replacements that rival or exceed the original parts. I designed these to be nearly an identical replacement, but with the advantages of modern 3D printing technology we can engineer materials that were previously impossible. I printed with NinjaFlex black TPU polymer (https://ninjatek.com/ninjaflex/), which is nearly indestructible (but a knife or scissors will cut it, just like rubber!), flexible, and quite gripping on most surfaces, you will be shocked at the improvement. This expensive material costs 3x other plastics, but there is really no alternative to get this strength and gripping flexibility. My first replacement designs were the ~100 year old squashed feet ones. These later German machines all have rubber that looks great--until you go to use it--so I didn't realize how badly they needed replacing as well. Even though the shape is intact, and it's not a brick, I found there is almost no traction on the original feet! The case feet were hard, and one was missing on each case for some reason.

A special feature is that this is an engineered material--the properties depend on the internal structure. These are printed with a solid shell, but inside there are layers printed with a 50% gyroid fill pattern, yielding more shock absorption and flexibility than the raw 85A shore hardness of the plastic. Some people may prefer the original dull rubber look, but I actually think these are a superior look to rubber, and the glossy finish accents the machine in a really nice way. I also think these will last far longer than natural rubber without compressing or falling apart.

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. I usually share my design files for others to print themselves if they have a printer, but in this case it was a very intricate design that I spent days iterating and working out, so I'm keeping it proprietary at least for now.

PS: Ebay's volume discount display is a bit confusing, each purchase is a SET OF FOUR typewriter feet + a SET OF FOUR  case feet.

Replacement installation is a breeze. On the machine, just unscrew the two screws retaining each foot, carefully remove the screws and save them. Be careful with the "shoe" or cover, on one machine they were metal, the other they were somewhat fragile plastic--clean and wax those while you have them off, clean the machine beneath them, and just reverse the procedure to install the new feet. For the case, I was able to pry all the old ones off with just my fingernails, and the new ones just push into place. You could use glue if you want, but they seem pretty snug on mine. That's it!

PSS: Note that the case feet have a different finish on each side, I chose the random pattern which kind of matches the case, but the other "octagram spiral" pattern would also be a nice accent, your choice. Also note my original case feet were dark brown, but you can't get this material in brown. I think black looks great.