Guess I should have gotten a more expensive thicker mat. The plastic deforms where the casters of the chair rest. So there is also some deformation of the carper underneath. But less than there would be without any chair mat.
As noted on the label it is for carpet that is 1/8-1/4 inch thick. Only use on Carpet tiles. If you use on regular carpet with a pad you will be unhappy. Since the mat is so thin wheels will indent and not roll freely.
These are great under our office chairs with wheels. We have several of these. They usually are sturdy & last for several years. But we replace them from time to time when they start looking dull. (Maybe you can scrub them to make them look brighter again but we just replace them.) So far…they have been reasonably priced at Staples.
I have now had my chair mat only a couple of days so I can't speak to its durability but so far I could not be more pleased. I can't imagine anything better.