They absolutely do the job. They make chair movements quieter. Seem to conform to different style leg ends and stay on securely.

Was not bad, just about 2 seconds of vibration. They help prevent rocking on slightly uneven floors.

One downside is that they are a little smaller than i had originally expected. As is typical today, i have to buy more than needed but these are nice to have around. My only complaint is they only have them in black.