2 mm thick sturdy plastic. I probably should have gotten the one for medium pile carpet. Maybe it won't indent as much where the wheels of my chair presses down on it. But the short pile one was cheaper so I got that one instead. Will see how long it lasts before these indentations turn into cracks. It was able to unroll and flatten itself in 24 hours in room temperature. Didnt like how the tape used to roll it up for shipping left a sticky residue though. Made in USA.
It's a nice thick material and a good size. My son uses it in his carpeted office and loves it. Easy to move his chair around and because of the thickness I feel it will last a long time.
Pros: The size was perfect. It fit just right underneath my desk. The studs are bottom made it impossible to slide around over the carpet. Perfect for daily tasking. Cons: This version is 100% see-through whereas my original one was translucent which looked neater over the carpet. I wish the mat would be firmer. Because with this softness over the next few years the chair's wheels will eventually puncture through the mat.