Simply unusable on carpet. Thin and sides move up when sitting in a chair on the mat. As the directions said I let it acclimate to room temperature for 24 hours. I put heavy books on the entire mat for 48 hours to flatten it out. Returned it right after.
I was surprised to receive my floor mat unpackaged with just a shipping label attached. Then I realized a "curl" would be a minor hassle. I used to sit and work at the computer I would find I had rolled back about a foot. I don't know the science behind this mat but my chair doesn't roll back with this mat. It's invisible on my oriental rug and doesn't shift around (there are nubs that are for that). Little gripper nubs that grab the carpet.