They advertise that they are for carpets over a half inch thick. Ours is 3/4". We are on our third one of these vinyl mats. They work for a while but eventually depress under the wheels of the computer chair and then the mat cracked and eventually pieces broke free. The first one was replaced after about a year but shipping was $30 so it wasn't exactly free replacement. We are just going with this one again because of the ease of purchasing it near our home. The polycarbonate mats are supposedly resistant to the breakage but are more costly. When this one finally breaks maybe we will try the poly ones.