Currently have mat on top of carpet. Chair's rollers tend to sink into the mat quickly so rolling can be difficult. It does protect the carpet (which was the goal). That said I'll probably invest in something a little better/thicker next time around.
I use this for my computer chair which I use about 3 hours per day. The mat protects the carpet and doesn't slide around. The main con about this product is that it becomes indented from the wheels.
Excellent just as described. Use at work on carpet - you would not be able to use this mat on hard floors - it has spikes on the underside to grip the carpet. mat is thick and durable. only dislike are the spikes they are sharp its large so it was hard to get into place but now that its there love it!
This is just the right size for working at my small desk but I have only had this a few weeks and already there are large dents in the mat where I apparently sit with the rollers in the same place every time I sit down to work... I have a feeling this won't last very long and am wondering if I should have spent a few more dollars to get a better quality one. It isn't digging into the carpet as much but I just can't see that it will last more than a year. Granted I am not a skinny person but I had expected better and have had better luck with other plastic floor mats.