I used them to move a heavy large screen TV, and a heavy table and they worked great. They are rated to hold 1000 lbs.
I lifted my furniture up and placed them under each leg, then lowered the furniture onto the disc. The weight of the furniture keeps them in place.
I paid $9.98 at Home Depot store. There are 8 in the pack.
These are made specifically for carpets
It would depend on the weight of the table. Extremely heavy items may crack the plastic on the bottom of the pads.
The packaging says for carpet only. I believe the have other ones for different surfaces.
I suppose you could id you didn't mind looking at them. Only left them under a bed frame because it's covered from view by the bedding.