The GREAT thing about this chair mat is that the points on the back of it DON'T HURT. They're flattened pyramids. An improvement that should've been made long ago.
An under desk carpet protector doesn't get any more basic than this. I've had it for about a month and it has performed fine. Although I consider these an expendable the test is how long it lasts before cracking into little pieces.
I am a 300 lb person who spends alot of time in front of my computer desk and my four roller chair glides easily and matt does not crack. Good investment for me.