AudioQuest : SorboGel Q feet 

AudioQuest's Q-Foot can breathe new life into your system by damping unwanted vibrations, allowing the system to sing deeper and further into the music. One particular place that we've found Q-Foot to be particularly effective is under any spinning mechanism, be it a disc player, turntable, or hard-drive/computer combination. Spinning mechanisms do not like their own vibrations, or others for that matter...

The shape of the foot makes a very big difference. The partial hole in the center increases compliance and horizontal surface. The extra vertical surface means more movement of the material is possible, and therefor more kinetic energy can be lost (turned into heat). The damping aspect of Q-Foot is often more important than the isolation ability ... though it is the non-specific frequency ability to both damp and isolate which makes Q-Foot so universally effective. Q-Foot are effective over a very wide band, the only strong caveat is to make sure that under a turntable or other more-than-average sensitive device, that the Q-foot are not pressed down on so hard that they lose their compliance. It's always more effective when there's "give" left, just more give is required to be most effective in such applications.