This chair mat fits my needs and is just the right size. Part of it goes under the desk where my legs and feet are and the rest of the mat is secured to the carpet by small plastic rivets to keep it from moving. Great product.
If you are looking for a mat that will have a stable surface over a deep pile carpet I highly suggest that you look somewhere else because after much time studying the catalog Staples offers this was the best I could identify and it is inadequate. Problem is that the plastic is soft and very pliable. The wheels of the desk chair sink in and form a deep pocket very quickly Then attempting to roll the desk chair to another position it's stuck in the pockets so moving takes more effort that anticipated. Many Years ago I purchased another high-end mat for my wife's desk I might have purchased it from Staples. It is over the same carpet: no issues; stable; no cracks; and flat.