For thick carpet needs deeper cleats. The chair wheels leave dimple marks in the surface and the wheel rolls back into the dimples so you are constantly moving the chair back into place.
It's rectangular that's what I like most about this mat. I got rid of my rug and replaced with is hardwood mat for easy cleaning to minimize fleas(I have pets)and dust mites accumulation.
I really like my mat--I just wish it wouldn't ruin so quickly. I had a huge hole in mine (but I think that is my fault since I have to roll around it so much all day long!). LOVE IT:)