CR-10 S4 40mm ball feet.

thingiverse

I made these feet because the ones I found online used extra screws. These are designed to just pop onto the bottom and use the single screw that holds the original feet in place. They are a very tight fit but do go on if you press hard enough. I'd suggest printing one out to begin with to see if it suits your needs. Again I was a bit too close with the tolerances but I managed to get mine to fit without too much trouble. They hold on very tight even without the screw in the centre. if you like them let me know! I'm always keen to hear feedback to help me improve my skills 3d printing. Thanks!