Ive been using ceramic balls for 6 months with no problems, the rings have a wear mark on them but its not a rough grove. I do agree that they don't stay super smooth for long but they have lasted much much better than the steel kit ones. I'm still on my origional plates from 12 month ago so I'll probably treat it to a new set over the holidays.
I've got the Hotbodies ceramics in my 501 and the TRF ones in my DB01 and they seem to be about the same quailty and the TRF ones are only £10 rather than the £18 I paid for the HB balls
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