Product review (5 stars): Genius!!!  Pure Genius!!!
These are un-freaking-believable!  I was very skeptical that these would work because of how violently my house was shaking due to my new front-loading washer I had newly installed on my second floor.  I just had my bathroom completely renovated and had a laundry room built in.  The washer is level and shipping bolts removed, but every single time it went into the spin cycle, it felt like we were having a 7.5 earthquake.  My entire house shook and I started to see my new grout in my new bathroom cracking.  New drywall was splitting at the seams.  Something had to be done.  It was either these silent feet or rip out the floor and reinforce it with more joists.  I opted for the feet...holy smokes!!!  They drastically reduce the vibrations.  I would say by about 90 percent.  Kudos to the inventor of these things!  I highly recommend them if your washer is driving you mad.