This chair mat says for up to 3/4" carpet. I measured my carpet and it is less than that. The chair mat has dents in it from the chair and does not allow the chair to move freely while sitting in it. I will be replacing this mat.
It may protect the carpet but its thickness (or thinness) allows it to compress into the carpet and thus makes rolling the chair around tough - i.e. the chair casters get hung up in the divots . . . or maybe I'm just too fat!