The soft plastic caps that came on the chairs, eventually gave out, and the metal chair leg frames were digging in to my hardwood floors.
This fits a chair with 25mm diameter round legs. The actual opening of the cap is 25.5mm in diameter.
Fusion 360 doc available, if you need to adjust the size.
I recommend printing in PETG with 100% infill up to at least 30mm height.
The author marked this model as their own original creation.