The BUT is that it seems much thinner than the 3.5-4.0 mm thickness which was discussed when I ordered it. I've put it on the carpet and it is in use but I worry that it will soon crack under pressure from my desk chair wheels. The previous two or three chair mats which I bought from STAPLES were 4mm thick and they would last maybe 6-7 years before cracking. Your on-line store person said this would be the thickest available. Dick Holliday