The mat is designed for medium pile carpets but is not firm enough to support my rolling chair. In less than two weeks of use the mat already has divots where chair wheels have rested making it difficult to roll the chair while seated.
If you are over 200 lbs and the chair mat is on a slightly flat carpet you may notice dents in the chair mat. The good part is the dent will go away but it does make it a little difficult to roll a chair back and forth. I bought the same chair mat for my granddaughter and she likes it.