Product review (3 stars): You must define "Vibration"
Ok, so I've had these installed a while for use with a 2nd floor front-load washer in a wood-frame building.

These claim to eliminate vibration, and they do... but understand what they mean by "vibration".

If your washing machine is "vibrating", they mean high-frequency vibration.  Think of your cellphone on silent mode.  Or maybe the feeling you get when you bump your elbow.  For that, they certainly do absorb nearly 100% of it.  I can't feel a thing more than 2-3 feet away.

However if your washer visibly *shakes* (oscillation of 1/4" or more) during its spin cycle, these may actually worsen the condition.  My washer (LG WM3455HW) doesn't have the greatest internal dampening, even when perfectly level, so once planted on these the high-speed spin cycle shook the floor a little more than previously!  Why?

These are made of a heavy gauge "goo".  If your washer heaves side to side at all, these "give" more than if it were sitting on the floor directly.  They aren't substantial enough to absorb that kind of deflection, so it transfers into the floor anyway.  The end result (for my washer) is it shakes side to side more drastically than it did before; and do does the floor

Whether or not that's a problem for you depends on your situation exactly.  If your washer actually 'vibrates' this work work great.  Otherwise, you may want to check into other solutions.