Thread here:
https://forums.arcade-museum.com/showthread.php?t=410081
Long and short, I wondered if 3/4" Delrin balls could be used instead of the traditional silver balls in my Hyperball. Was just looking for something to provide a better contrast with the black playfield. So, I ordered 50 of them (game takes 55).
Had my doubts (weight and auger issues) but - they work! Not only that, they look to hold up well AND significantly lower the noise of the machine.
Vid in thread.