Product review (5 stars): Surprised how well these worked.
I installed my new Samsung front load washer on a concrete slab.  First run the washer was jumping up and down even though I had spent a considerable amount of time leveling the damn thing.  After 5 more attempts at leveling to prevent jumping and walking, I gave up and decided to try these based on other reviews.  I was surprised at how well these worked.

The picture doesn't show the actual size, so I was concerned these would be the same size as the existing feet on the washer.  These are actually larger than the the feet in diameter and about 3/4 inch tall.  After installing my washer stopped walking across the floor. These don't stop the wiggle when the spin cycle starts, but they do help to reach the balanced spin and the washer no longer walks across the floor.  I've set the dryer about three inches from the washer to keep them from banging together when the spin cycle starts.

Will have to see how long these last since I just installed this week.