This mat is not strong enough to prevent a chair from quickly wearing grooves and dimples in it. These slowly worsen eventually causing the plastic to crack. It is good for a few months of full time use at most.
I didn't think there would be a difference between flat pile and low pile carpet for this chair mat but there is. My chair made big dents in the mat and wouldn't roll at all (I am a petit woman). My carpet is very low pile but not flat. Unfortunately Staples doesn't sell any other kind of chair mat with a lip in their stores.
When it was left on my porch it was draped across the box my chair came in. Took a couple days for the folds to completely disappear. Wheels of the chair don't seem to be leaving indents and I'm at the upper range of the chair's rating.