This Carpet Chair Mat has been under our desk chair for a year. The mat moves around on my 1987 medium pile carpet. However it provides carpet protection & allows chair to move around without the mat being depressed--which is good.
I see where other customers experienced poor chair rolling cracked mats or moving mats (prongs not long enough to keep mat in place). I purchased two of these mats for two different office chairs/desks. For me the mats are working well. They are staying in place and my chairs are moving quite freely--to the point where I must keep them from rolling from under me (lol). I'll give it some time to see if I experience any cracking but so far no cracks.
I put the mat down and put my office chair on it and have been sitting in the chair and wheeling it around for about 4 days now and so far it's working fine. The mat is softer than some but so far that isn't interfering with my use. For the price I'm very satisfied.