Bests & Worsts Reviews from Amazon

The mat is delivered flat. I followed the instructions before ordering where I measured the depth to the sub floor. What a waste of time. I expected the grippers to point down at least a half inch or more, but they are just dimples that somewhat hold the mat in place. I am not heavy but the chair does curve the edges of the mat up when it nears the edges. So all in all it does the job, but nowhere near as firm and robust as I was led to believe. Update: the dimples DO NOT hold the mat in place!