piano noise keeper and sound proof caster cups extreme testing

We are testing two caster cups mainly on the catching of sound escapement.
1) piano noise keeper
2) sound proof caster cup
Both are excellent on absorption of impact noise but sound escapement will depend mainly on the environment setting.

[@teegees]

Lots of weird noise suddenly when caster cups are used

[@NelsonYum]

What caster cups are you using?