It is made for very thin carpet. While rolling over with an office chair the mat moves; after it has moves three inches I have to reposition it. The reason it moves: the protruding fingers on the back-side are way too short and not pointed enough to grip into normal carpeting.
I learned the hard way to put a mat down under my computer chair - I've had a couple from Staples I wanted the type of mat that has the pointy knobs on the bottom so it doesn't slide all over the floor. This works great and the price was reasonable.