It fits to controllers that have already had the plastic ring underneath the d-pad removed as part of adding a transforming d-pad.
After my 2nd transforming D-pad broke I looked for something different and found these singular button per direction stls.
I tried Courior_6's one, but found it to be too big to fit my controller.
So this is a remake of that design, made thinner and shorter to fit, I have also added the relevant cutout and locating protrusions to the bottom so no extra modifying was needed and the original d-pad can be refitted if needed.

None of this is my idea, this is just of remix of the other designs, Altenife appears to be the first.
If you need guidance on removing the plastic ring, CarolinaGamer has an excellent video on youtube.

All files updated, I added small chamfers around the bottom of the button holes in the hub to aid in cleanup post printing, increased the fillet size around the top of the curved button tops and cleaned up some of the geometry between the buttons and hub parts.
No further modification planned, personally I settled for curved buttons for left/right and mid-curved for up/down

No

0.12

20%+

After printing I concentrate on the buttons, shaving off the layer lines around the button shaft that rubs the hub, and blend the layer lines together on the top of the curved button for more comfort. Also clear out any first layer squish from the button holes in the hub.