The chair mat "walks" with use the cleats or studs do not extend out far enough to prevent it from walking across the floor. It says for carpets up to 1 inch but would only work on very short pile.
First I have to say that the 48" dimension included the lip which is not what I expected. Next the mat does dimple with my 185 pound weight. If this matters to you then don't buy this mat. Spend the extra money and get a better one.
Good size but When put on carpet even a somewhat firm carpet the plastic dents and doesn't let my chair move well. The wheels get a bit stuck in the plastic which becomes dented.