My carpet is not totally flat but a very low pile carpet. This mat is too thin for even low pile. The feet of my chair make impressions in the mat after sitting for a while in one spot. Read the description with that in mind.
The mat is good saves carpet. However this is at least the third one i have had. After about a year they start tp crack. I used them on very low pile carpet as directions say. On a 1 to 10 rating ill give it a 8