I did need twice of how for a largest my chair needed on top of a rug this idea did the well very well. As usually got my idea at the Staples for my idea get there and get the best!
I'm using on a medium pile carpet. Yes it dents and shifts a bit but they all do on medium carpet. I don't mind moving the mat back every few days. The material is a softer vinyl than my old one so I expect it won't break as readily. Dents are OK breaks are not. I wanted something inexpensive for a year or so until I move and this one will do OK.
Went to purchase chair mat in store. This was only model they had. Too thin. After only a few hours rollers on chair created permanent divots in mat. total waste of time and money.
Super thin mat not really great for carpet as the wheels sing in and prevent chair from moving freely. However it does protect the carpet so it gets 2 stars for that.