Product review (5 stars): Worth Every Penny
I looked at these a year ago and thought $40 was kind of pricey for four molded pieces, so I decided to try to make some adjustments to the washer to improve.  It helped, but the floors upstairs still would shake and the noise was still unacceptable.

I finally gave in and ordered these last week and installed them today.  It was a quick install.  Simply rock the washer forward and slide the cups under the back, and then vice versa for the front.

Good grief, they work great!  If I'd known how well these work a year ago, I'd have bought them then.  I've been testing them all day, running jeans, then blankets, towels, etc.  When I'm in another room, I can't even tell when it's in the spin cycle.  Sitting downstairs, it used to be easy to tell; not any more.

If you're sick of finding a new area of the floor creak, buy these!