The mat's knobbies on the bottom are just right but it didn't flatten out all the way yet. I have had it a week. Took 2 days just to get the thing to unroll and then I had to point a heater at it. Maybe this summer it will finish flattening....
The mat is exactly what we needed to protect the carpet under our office chair. It is a great size good quality and stays in position. It was delivered quickly!