I think my carpet is a medium pile and I have been using this chair mat for a couple of weeks and it has some pretty serious dimples where the wheels of the chair sit. I make sure the chair is not in exactly the same place on the mat as I believe that would make the dimples worse. I will keep an eye on it and update in the future.
The product description said this product would be fine with pile carpets. It is not stiff enough - so the chair creates dents in the mat. They are not permanent but with a rolling chair you are constantly stuck in the valleys that it creates.
Arrived in time - bend like hell. Mat is to thin and moves spikes are way to short to have any effect. Chair wheels dent the mat very heavily - makes moving the chair around difficult at times. Does not work well on thicker carpets. Not worth the money.
This is a replacement for an older one which after years of use wore out. I would not have purchased it a second time if I were not satisfied with the product.