Piezo, Yup! Hard to believe. I was forewarned of this mechanical break-in period prior to installing them under my rack and speakers.
But I paid no attention to it whatsoever as I found the notion perhaps even silly and forgot about it immediately. But lo and behold, one day soon thereafter, I turned on my system and there were vast improvements. The micro-dynamic improvements were on the order of about 30% and the macro-dynamic improvements were perhaps about 15%. This is assuming that a 5% sonic improvement is barely audible. And those percentages do not take into consideration the initial 5% to 10% improvements immediately after installation.
Of course, after hearing the drastic post break-in improvements, I then remembered the warning of the break-in period.
That's why when somebody says this rack is better than that rack or these points are better than those points, I'll bet dollars to doughnuts, the evaluator never took mechanical break-in into consideration.
And perhaps that is one reason some to many have yet to appreciate the sonic advantages of coupling over decoupling.
-IMO