Try'd cheaper mat first. Measure carpet as instructed and should have worked. Couldn't tell any difference from directly on carpet. Went back and bought best they had. Chair still leaves indents and hard to move when set in one spot. Was expecting to be more rigid.
Let me lead off by saying this is not a commercial grade mat but is perfect for the home setting where it will not be subjected to continuous use. It is a good quality product and is good for bear or carpeted floors.
Not a good purchase. as it is very thin actually moves on the rug and the 4 casters of my "swivelling" chair get stuck. Its predecessor did none of those and lasted 7 years!