Product review (5 stars): Dampens vibration well
We recently bought a new LG front-loading washer and dryer.  Not wanting to spend $400 for the manufacturer's pedestals, I built my own.  Since I built one pedestal for them both to sit on, the vibrations generated by the washer would shake the dryer, causing some loud bangs.  I thus purchased a set of these feet for each one.

These feet have reduced the severity of the transferred vibration to tolerable levels (i.e. no more noises from the dryer).  When the washer is vibrating most forcefully, you can visibly see these feet compressing (and thus absorbing the vibration).  I was hesitant to buy these due to the cost, but the materials for the pedestal I built plus the cost of these was still less than half of what I would have spent on the manufacturer's pedestals.