Noise damper too.

I went to see what it would cost me to have my printer more quiet while working, all that vibration on some Aluminium legs against the desk wood surface was acting like a guitar amplification effect, and the prices made me invent someting cheaper, those cups are held with a bolt and a nut in the Aluminium profile ditch, and the ball sits in by pressure (the hemisphere is not at 50% but at 55%, hence a bit tight to fit in the ball)

I have being using the printer like this for 4 years now, sometimes printing non stop for 96 hours, and I sleep likle a baby next to it.

Yes they work, they are cheap PLA and cheap tennis balls. Total less than 5 dollars and there you have it.

For the price you have access to download the STL file that you can print yourself.