Not wanting to damage the carpet pile under my rolling office chair I checked out Staples and found the 36" x 48" clear mat which is a perfect fit and my chair rolls easily on it.
I bought this product because of the majority of the reviews were great. A few did remark of how the mat gets indentations from the chair rolling on it. Which I am gaving problems with. Also the mat constantly moves. I am not happy with my purchase. Wish I could return it!
The "Staples® Flat Pile Carpet Chair Mat 36" x 48" Lip" isn't a great fit for the L-shaped desk I have. It fits just right up against the sides of the desk so I can't go a size larger; however the lip isn't wide enough and the front right wheel tends to fall off. I also find that if I roll too far away from the center of the desk the back wheel falls off the mat. If I had the keyboard installed in the corner of the L-shaped desk this would not work at all. However it works sufficiently since the keyboard is located facing forward.