The mat locks perfectly into our extremely low-pile non-padded berber carpeting. I've used it for 2 weeks now and no deep indentation from the chair. If I do get a slight indentation it's gone the next morning.
Protects the carpet decent chair mat. I wish it was a tiny bit thicker. I weigh 200 lbs and after sitting for a few hours the mat does develop some leg divets. The go away by the next day but they are annoying after they've developed and you want to move your chair while sitting.