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.
Followed the instructions for installing and the mat flattened out nicely. The mat appears to be heavy duty and should last a "lifetime " if not it will be returned for replacement. I made sure to save all the paperwork and receipts. I would recommend this product.